CA2288608A1 - Full featured data access arrangement for use with modems - Google Patents
Full featured data access arrangement for use with modems Download PDFInfo
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- CA2288608A1 CA2288608A1 CA002288608A CA2288608A CA2288608A1 CA 2288608 A1 CA2288608 A1 CA 2288608A1 CA 002288608 A CA002288608 A CA 002288608A CA 2288608 A CA2288608 A CA 2288608A CA 2288608 A1 CA2288608 A1 CA 2288608A1
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- Prior art keywords
- hook
- modem
- circuit
- daa
- data access
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
- H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
Abstract
A full-featured data access arrangement (DAA) for connecting a modem to a public switched telephone network (PSTN) includes a bridge current loop circuit, a line in use detection circuit, an off-hook relay, a loop current sense circuit, and an extension/remote event detector circuit. The off-hook relay is connected in series with the current loop circuit to enable the DAA
to detect external off-hook and on-hook events when the modem is in an on-hook state. The DAA is configured to detect the off-hook and subsequent on-hook status of an extension telephone at a location even though the modem and a handset sharing a line connector with the modem are both in an on-hook state.
The DAA is also capable of detecting an off-hook state of an extension telephone even though the modem is in an off-hook state. In addition, the DAA
can detect when a remote telephone device that initiates an incoming call is placed on hook.
to detect external off-hook and on-hook events when the modem is in an on-hook state. The DAA is configured to detect the off-hook and subsequent on-hook status of an extension telephone at a location even though the modem and a handset sharing a line connector with the modem are both in an on-hook state.
The DAA is also capable of detecting an off-hook state of an extension telephone even though the modem is in an off-hook state. In addition, the DAA
can detect when a remote telephone device that initiates an incoming call is placed on hook.
Description
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FULL FEATURED DATA A: CFlSS ARF.AN~EMEN~ ' ~ "
FOR USE WITH MODEMS
Inventor: Jeffrey Lee .a The present inventio=. relates, generally, to data access arrangement (DAA) devices, sometimes referred to as direct access arrangement devices, for connecting a telephone device to a telephone network and, more particularly, to a full-featured DAA configured to support evolving telephony industry standards.
Background Art and Technical Problems The Telecommunications Industry Association (TIA) and the Electronics Industry Association (EIA) from time to time promulgate non-binding technical standards for equipment sold in the telecommunications industry. While compliance with these standards by product manufacturers is generally voluntary, the practical importance of producing equipment in compliance with TIA/EIA standards is becoming increasingly important. In addition, the Federal Communication Commission (FCC) from time to time publishes binding regulations governing the telecommunications industry to ensure safety, compatibility, and to minimize problematic - interference among various electrical devices and components sold in the telecommunications industry.
In particular, Part 68 of the FCC Guidelines relates to such matters as, for example, the requirement that telephones and other telephone devices be electrically isolated from the telephone network to prevent shock, fire, and other environmental hazards from effecting the users of such equipment. In this context, the term "telephone device" can refer to telephones, modems, personal computers (PCS), fax machines, telephone answering machines (TAM), and the like, which are typically connected to a telephone line through a conventional RJ-11 telephone jack.
Recently, TIA/EIA Standards Proposal No. 3131-A was approved and published as TIA/EIA-695 which relates to, inter alia, various functions to be supported by data access arrangement (DAA) devices, also commonly referred to as direct access arrangement devices. In -~- particular, a DAA is a device which connects a telephone device, e.g., a modem, to an RJ-11 type _..
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_ __ ___ _ ' 20944.0516 < ,., r. r r ., I~ n cr ~~ _. ~ cr o ~ r r, ,. , .. ~. r r. n n ~ ~ n n r c: f n n t, .. n r, r c' c' ~. , .. ., jack, to thereby provide an interface between the m~demand tl~,laub~ie Switc'~r~ Telephone I~etwork~ -(PSTN). The DAA suitably includes an appropriate opto-electric or other isolation device to isolate the PSTN (which typically operates in the range of 42-200 volts) from the modem (which typically operates in the range of about 1 to 3 volts peak to peak). The transformer circuit within the DAA
which performs this voltage step-down function is often referred to as the primary transformer, or One of the principle functions of a conventional DA_A surrounds the ability of the DAA to w detect an incoming ring signal. When a ring signal is detected in a conventional telephone handset, the user can simply lift the telephone handset from the receiver, whereupon the telephone is said to go "off hook". Upon assuming the off hook position, the "off hook" relay within the DAA closes, thereby establishing a connection between the telephone handset and the telephone device which generated the incoming call. When the telephone call is finished and the user places the handset back onto the receiver, the handset is said to go back on hook, whereupon the off hook relay with?.n the DAA is open, terminating the connection.
In a modem context, upon detection of a ring signal, the DAA may be configured to transmit a ring detect signal to a controller associated with the modem or with the PC
with which the modem is associated, whereupon a control signal is applied to the DAA's off hook relay, closing the relay.
Upon closure of the off hook relay, a data communications path is established between the modem and the telephone device which generated the incoming call.
Many modems in use today, particularly modems associated with PCS, also include a local handset connection, such that both the data modem and the telephone handset are connected to the telephone network through a single, shared RJ-11 phone jack or other interface device. In this context, it will be understood that the term "telephone handset" can include audio speakers, a headset, a voice activated speaker phone, a condenser microphone, or virtually any other audio configuration which permits voice or audio transmission. Moreover, it will also be understood in the context of the present invention that the term "local handset" or "local device" refers to a telephone or other device which shares a common RJ-11 type device with a modem, whereas the term "extension handset" or "extension device" refers to a telephone device which is connected to a common telephone line (for ' 20944:0516 ' ' . , c ~. ~ , ..
n r .. r. n ~ n t? ' ,, C r.. n example, in another bedroom of the same home) bud which has its own-IFJ-11 type phone jack (:.~~, tho. ' extension telephone device does not share a common RJ-11 connection).
DAAs for use with a modem having a local handset are generally well-known, for example as described in Chapter 6 of the "K-Series Design Manual" published by Silicon Systems. Presently known DAAs, however, are unsatisfactory in several regards. For example, while a presently known ass cia -modem is off hook, many known DAAs are unable to detect an extension device off hook condition while the modem is on hook. Moreover, to the extent a presently known DAA is able to detect when an extension device goes off hook while the modem associated with the DAA is on hook under certain circumstances, the DAA is unable to ascertain when the extension device goes back on hook. One such DAA is disclosed in PCT application WO-A-95 14 344. In that application a telephone line monitoring circuit~for a modem monitors the tip and ring lines of the telephone line. A
first circuit detects when a local phone (extention phone as that term is used in the present appliction) goes off hook while the modem is on-hook by sensing a decrease in a differential voltage between the tip and ring lines. A
second circuit detects the pick up of a local phone while the modem is off hook by detecting a change in the impedance between the tip and ring lines. A third circuit detects the hang up of a remote phone connected with the modem while the modem is off=hook by detecting a temporary break in the DC
loop between the central office and the modem. The application does not disclose a circuit that detects whEn the local phone returns on-hook, either when the modem is on-hook or off hook.
A full featured DAA which overcomes the shortcomings of the prior art is thus needed.
The present invention provides a full-featured DAA for use with a modem which overcomes many of the shortcomings of the prior art.
Summar~of the Invention The present invention provides methods and apparatus for interfacing a phone device with a telephone network in a manner which overcomes many of the shortcomings of the prior art.
In accordance with a preferred embodiment of the present invention, a DAA
circuit is provided which detects when an extension telephone device goes off hook while the modem associated with the DAA is on hook, as well as detecting when the extension device goes back on hook. The ability of the ~
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subject DAA to detect when an extension device goes bask on hook is~paiticulara;z irrige'riant, ina.~muc~?~1., "
as it permits a facsimile or other data packet which is desired to be transmitted to be queued and transmitted from the queue once the extension telephone device goes back on hook.
In accordance with a further aspect of the present invention, when the modem with which the DAA is associated is in the off hook condition, the DAA is configured to detect when an extension the PC to which the modem is associated. In this way, the user can be informed that the modem connection has been terminated because of an extension off hook condition, as opposed to other common causes for modem disconnections, including Internet service provider (ISP) failure, line failure, local hard drive failure, or the like.
In accordance with a further aspect of the present invention, when the modem is in the off hook condition, its associated DAA may be configured to detect when a remote telephone device (i.e., the telephone device from which an incoming telephone call has been placed) is hung up. This permits a modem, for example operating in the TAM mode, to terminate the connection when the remote telephone device hangs up, thus avoiding the familiar but annoying dial tone which is often inadvertently replayed by many TaM users when checking their telephone messages, as a result of the recording device associated with the answering machine commencing its recording sequence immediately before the calling party hangs up.
In accordance with a further aspect of the present invention, many of the foregoing functions may be conveniently implemented in software, thereby providing an efficient, low cost, TIA/EIA
compliant DAA useful with current and future generation modems, including but not limited to the new 56kbps modem technologies currently emerging, for example the new 56K
modem chip sets ' produced by Rockwell Semiconductor Systems of Newport Beach, California.
Brief Description of the Drawing Figu The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like numerals denote like elements, and:
w Figure 1 is a schematic block diagram of an exemplary DAA circuit interconnecting a modem hybrid circuit with an incoming telephone line;
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n o o c ~ r, n r. c c n ~ r, r, Figure 2 is a schematic, functional block diagram of amerhaaaed DAA~circui*_ illustratsxig ate, arrangement of voltage and current detection components which provides enhanced event detection functionality to a DAA;
Figure 3 is a schematic block diagram of a single telephone line having a plurality of telephone extensions;
Figure 5 is a schematic circuit diagram of an exemplary line in use detection circuit;
--~ Figure 6 is a graphical depiction of the output signal generated by the line in use circuit of Figure ~;
Figure 7 is a schematic diagram of an exemplary embodiment of a line current sense circuit;
and Figure 8 is a graphical representation of an exemplary output of the line current sense circuit shown in Figure 7.
Detailed Description of Preferred Exemplary Embodiments Referring now to Figure 1, a conventional DAA 10 suitably connects a modem 12 to the Public Switched Telephone Network (PSTN), Private Branch Exchange (PBX), or the like.
As is known in the art, the incoming signal from the PSTN/PBX is typically carried on a pair of "wires" referred to as the tip and ring lines 18 and 20; respectively. TI=us, the tip-to-ring voltage is typically expressed as V tr. -Modem 12 suitably comprises a modem hybrid 14 and a voice hybrid 16 to facilitate the transmission of both voice and data through the same modem 12. Although modem hybrid 14 and voice hybrid 16 are illustrated schematically in Figure 1 as separate functional units, those skilled in the art will appreciate that the data and voice functions of modem 12 may suitably be integrated in any desired manner.
With continued reference to Figure 1, a preferred embodiment of the present invention is - suitably implemented in the context of a modem which includes a modem (or data) hybrid~component -and a voice hybrid component, such that the single modem can support data, facsimile; and other non-voice transmissions through incoming lines 18 and 20, as well as voice and other audio transmission 20944.0516 ~ ' n ~., ., .. _ . o ., . .
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' through voice lines 22 associated with a local hand set 16. In ~Li:s c~rtext, if wili be. ~zndersto~d that local handset 36 is connected to the PSTN through an RJ-11 type connector which the handset shares with DAA 10: In accordance with a particularly preferred embodiment, it will be appreciated that both voice and data is suitably transmitted to and from the PSTN through tip and ring wires 18 and 20.
More particularly, a voice relay circuit 24 is suitably configured to permit either the (simultaneous voice and data) function associated with conventional modems or, alternatively, voice relay 24 may be-configured to permit a transmission of data only or voice only.
With continued reference to Figure 1, a ring detect circuit 28 is suitably configured to detect the presence of an incoming "call" through the PST'N from a remote telephone device, i.e., a remote modem, fax machine, telephone handset, or the like. When an incoming call is detected, ring detect circuit 28 suitably sends a signal to modem 12, whereupon a signal may be applied to off hook relay 26 to thereby close the relay and accept the call. Once the call is accepted, the incoming AC signal is applied to modem 12, and a DC component of the incoming signal is transmitted through bridge circuit 30 to a DC current sink circuit 32. During a call connection, DC
current sink 32 suitably consumes a DC component of the incoming signal sufficient in magnitude to permit the detection of the call connection by the local exchange carrier (LEC) or the local Central Office (CO). When the -_ call is terminated, i.e., when off hook relay circuit 26 is again opened, the DC component transmitted through bridge circuit 30 is essentially terrlinated, allowing the CO to detect the completion of the call.
With continued reference to Figure 1, an event detection circuit 34 is suitably employed to monitor the magnitude of the loop current in DC current sink circuit 32, to thereby detect an off hook condition of an extension telephone device (e.g., by detecting a change in the loop current as a result of an extension off hook condition).
With continued reference to Figure 1, many conventional DAAs are configured such that off hook relay circuit 26 is in series with the incoming telephone line, as shown in Figure 1, as opposed to locating the off hook relay within the current sink loop connected to bridge 30. Consequently, for those DAAs wherein the off hook relay circuit is located in the incoming telephone line as shown in Figure 1, the DAA is typically only capable of detecting an extension telephone off hook condition when the modem is in the off hook condition (i.e., when off hook relay 26 is closed). Stated another °~'. ~."r . .:__......_..~__. .. o . .. .. ....__._.._.._...
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i o , ..0 0 0 . r~ " ,. r. r, p c, ~ ~ n o o r. i: r. ~ , ~ ::~~ nn, way, it is necessary to establish a modem connection as pree~i?ditec~ri to tlie~aliility~of the LaAA t~~ ' detect certain external events, such as the off hook condition of an extension device, a hang up .. :~ec~a~:~.'..- . .-. c condition of a remote telephone, or the like. Moreover, the configuration of the off hook relay as shown in Figure 1 generally precludes the DAA from detecting many of these important external events when the computer associated with the modem is off or if a modem connection does not exist.
._ , suitably includes a caller ID relay 208, a ring detect circuit 220, a bridge 210, a bridge current loop circuit 222, a line in use detection circuit 212, an off hook relay 214, a DC
current sink circuit 216, a loop current sense (LCS) circuit 217 and an extension/remote event detector circuit 218. In addition to performing many of the functions set forth in TIA/EIA-695, DAA 202 suitably supports many of the existing functions associated with conventional DAAs, such as isolating modem 204 and its associated local handset 224 from the high voltage environment of the PSTN.
-- , With continued reference to Figure 2, off hook relay 214 is suitably connected in series with , - current sink loop 222, as opposed to being disposed in series with the incoming tip and ring lines, as is the case with may prior art DAAs. This improvement has substantial implications, as discussed in greater detail below, in that it permits DAA 202 to detect various external events even when a modem connection is not extant (i.e., even when off hook relay 214 is open).
With continued reference to Figure 2, those skilled in the art will appreciate that a caller ID
(CID) signal is generally transmitted from the LEC between the first and second audible rings. In accordance with a preferred embodiment of the present invention, ring detect circuit 220 is suitably configured to detect an incoming call, whereupon DAA 202 is advantageously configured to capture the telephone number or other indicia associated with the incoming call, via ring detect circuit 220, °
CID circuit 208, or through any other convenient mechanism. Once the ID of the incoming call is captured, it can be compared with a look up table stored in memory associated with the modem, or otherwise evaluated to determine whether the modem desires to accept the incoming call. For example, a list of destinations from which the modem desires to accept calls, or a list of destinations from which the modem desires to reject calls, or both, may suitably be compiled and stored in memory; for example in the form of a look up table. When the ID of the incoming call is captured arid compared to the look up table, the call may be accepted or rejected, as desired.
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If the call is to be accepted, the controller (ziot s'iown)<a~;;ocrated wits ~riodem°204 sen.:crs aa~~ °
appropriate signal to CID circuit 208, thereby closing the relay. The modem is also configured to transmit a signal to off hook relay circuit 214 to close the relay and thereby establish the call connection.
Once a call connection is established, bridge circuit 210 drops the line current, and converts a b 7 detectable by the Central Office (CO), such that the Cn can determine that the call connection has been made. The remaining AC component of the incoming signal is suitably applied to the modem hybrid circuit.
With continued reference to Figure 2, DC current sink circuit 216 suitably comprises a line current sense detector 217 for detecting an off hook condition of modem 204, while circuit 226 suitably comprises a loop current sense detector 227 for detecting an off hook condition of handset 224. In accordance with a particularly preferred embodiment, if during a modem connection the user desires to integrate voice into the transmission, the user may press a suitable function key or otherwise interact with the modem (or its associated PC), for example by depressing a predetermined key on the keyboard associated with the PC. In this way, the SVD function may be implemented, causing the voice relay circuit 228 to integrate the handset into the modem connection.
In accordance with a particularly preferred embodiment, when LCS circuit 226 detects the off hook condition of local handset 224, DAA 202 suitably signals the modem controller to initialize the SVD function.
In a particularly preferred embodiment, line in use circuit 212 is suitably implemented using a TMOS or other suitable, inexpensive electronic component. This is in contrast to prior art systems, which typically detect an off hook condition of an extension telephone device using a comparator circuit. By integrating the TMOS circuit into line in use detection circuit 212, the need for a-comparator circuit and its associated high cost is also eliminated. Moreover, the use of a TMOS or similar device draws very little current, for example on the order of 5 microamps, which further .
facilitates compliance with FCC Part 68. -In accordance with an alternate embodiment of the present invention, the subject LAA maybe °' configured to detect an off hook condition of an extension telephone device even when the modem hME~~~DEa SHcE!' 20944.0516 ~ ' ' ' a ~ nn ;,~ u~:
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remains off hook. Referring now to Figure 3, an i icorriing call~froin, tie Centc~r0f~ce (CO) X02 ia, suitably applied to a single telephone line 304 associated with a home, small office, or the like. In the illustrated. embodiment, the single phone line 304 suitably has associated therewith a plurality of extensions, for example a first extension 306 located in a bedroom, a second extension 308 located in the kitchen, and a third extension 310 which is suitably dedicated to a PC
having a local handset 312 , RJ-11 connection to the telephone line 304. When both the local modem and local handset associated with extension 310 are in the on hook condition, conventional DAAs associated with the modem at extension 310 are typically incapable of detecting an off hook condition of an extension handset, for example, in the kitchen. In order to detect an off hook condition on an extension telephone device while the local modem and local modem handset remain on hook, it may be desirable to incorporate a voltage detector circuit, for example as shown in Figure 4, to detect a reduction in voltage (or current) as a result of an extension off hook condition. More particularly, an extension off hook detector circuit 404 suitably comprises a storage capacitor 406 corresponding to an analog memory component, a detector circuit 408 having an output signal 410 associated therewith, and suitably configured to detect the tip-to-ring voltage associated with telephone line 304, which voltage is known to drop upon the occurrence of an off hook condition of any extension telephone device. However, it will be appreciated that sensing circuits such as that shown in Figure 4 are not readily capable of detecting when the extension telephone device goes back on hook and, hence, such circuits are of limited utility.
Returning now to Figures 2 and 5-8, a number of particularly preferred embodiments of the present invention suitably provide apparatus and techniques for detecting an off hook condition of an extension telephone device, as well as the return of that device to an on hook condition, regardless of whether the modem associated with the DAA is on hook or off hook.
With reference now to Figures 2 and 5-6, line in use detection circuit 212 is suitably co~gured to detect tip-to-ring voltage (or a scaled component thereof), for example within current loop 222. Line in use circuit 212 is also co~gured to generate an output signal 510 which, in the illustrated embodiment, is essentially a binary oa~put signal. Output signal 510 is suitably applied to the modem _ 20544.0516 ' ' ' ' n ;, .. ,.. , o n . . ~ 1 c. ,~
n . ~ n , ~ tv " , r' ~ o o , ~ ~ r controller (not shown) to indicate to the controller v!~ether the line r,s i~.
use, i. e: ,.vrhefber any exterisior~.
device is off hook, as described in greater detail below.
With continued reference to Figures 2 and 5-6, circuit 212 suitably comprises respective first and second resistors R1 and R2, respective first and second switches SW1 and SW2, respective current paths 504 and 506, and an opto-isolator element 502. It should be appreciated that the values of a wide variety of telephones, telephone lines, and telephone systems (i.e., PBX, PSTN, public telephones, and the like) to effect a change in output signal 510 upon a drop in tip-to-ring voltage Vtr.
With specific reference to Figures 5 and 6, output signal 510 applied to the modem controller is suitably high when no extension devices are in the off hook condition, whereas output signal 510 i~ suitably low when any extension (e.g., extension 306 or 308 in Figure 3) is in the off hook condition. In contrast to the voltage detection circuit illustrated schematically in Figure 4, the line in use detection circuit 212 shown in Figure 5 follows Vø in essentially real time, i.e., without the delay occasioned by capacitor 406. When no extensions are off hook, V« is high, such that SW1 is closed, causing current to flow through path 504. As a result, S W2 remains open, such that no current flows W rough path 506. With no current flowing through path 506, the opto-element 502 remains disabled, such that output signal 510 is pulled high. When an extension telephone device goes off hook, causing a drop in Vtr, SW1 opens, terminating the current flow through path 504. As a result, SW2 closes, producing current flow through path 506. The current flow activates opto-element 502, energizing the LED associated with the opto-element, such that output signal 510 is driven low. This phenomena is graphically illustrated in Figure 6, where time t~ corresponds to an extension telephone device going off hook, and the interval between times t, and t2 corresponds to the period in which an extension telephone device remains off hook.
In this way, the subject DAA set forth in Figure 2 and as explained above in conjunction with Figure 5 is capable of communicating to the modem controller a signal (signal 510) any time an extension telephone device goes off hook; while modem 204 is on hook.
Moreover, it will be appreciated that when the modem is off hook, i.e., during;a modem connection, the modem connection is typically terminateu when an extension telephone device goes off hook. This is analogous to a situation where a user of a PC (i, e., PC 310 in Figure 3) is involved in an online session (e.g., with an _ -10 _ _ ._ _ .. _ ._ . .._ _.
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r: .7 .C C c .i ~~ n p i :.n external ISP), and during the modem session, sorleor?e else .i~~tfi~ (louse 'u~vi~it~l.~Qiy picks.up ~, telephone in the kitchen (extension 308) or in the bedroom (extension 306). As a result, the modem connection is typically terminated, as distinguished from the situation where handset 312 may go off hook without terminating the modem session inasmuch as handset 312 and modem 310 enjoy the same RJ-11 connection to the telephone line. Notwithstanding the fact that the modem session may be ~tel<minated~~hen an PxtPn~ion telep one set goes off hook it may nonetheless be desirable to detect ' the off hook condition of an extension telephone set during a modem connection, as described below in conjunction with Figure 7, so that the PC user may be apprised of the reason for the termination of his modem connection; that is, it may be desirable for the PC to signal the PC
operator that the connection is terminated because of an off hook condition at an extension, so that the PC operator does not erroneously presume that the connection was terminated because of an ISP
failure, hard drive failure, line failure, or some other reason.
Refernng now to Figure 7, the loop current sense (LCS) circuit 217 of current sink 216 is suitably employed to detect an extension off hook condition when the modem is off hook, i.e., during a modem connection. The loop current sense circuit 217 suitably comprises an opto-isolator element 704 configured ~o generate an output signal 706 indicative of the state of loop current sense detector circuit 217. More particularly, the output of opto-isolator 704 is suitably pulled high (i.e., pulled to V~~. Thus, when modem off hook relay 214 is open, i. e., when the modem is in the on hook condition, output signal 706 is suitably high: When the modem goes off hook, relay 214 closes, producing a current flow through the opto-isolator 704, thereby driving output signal 706 low. . With momentary reference to Figure 8, output signal 706 is suitably high prior to time t," i.
e., while the modem is on hook. When the modem goes off hook at time tA, output signal 706 drops, as described' above. If the modem thereafter stays off hook, it is desirable to detect when an extension telephone device goes off hook while the modem remains in the off hook condition.
With continued reference to Figures 2 and 7-8, time tB suitably corresponds to an extension telephone device going off hook while the modem remains off hook.
Surprisingly, output signal 706 goes back high, even though the modem remains off hook (i.e., even though relay 214 remains closed).
Of course, if the modem were to go back on hook, i.e., if relay 214 were to open, output signal 706 _._ -____.__.~. . ,qMFNDED SHEET
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would also go back to the high condition, inasmuch as the curs°.~it vc~;i?.ld stop ~:oW rg Through opto-device 704, thereby driving output signal 706 high.
As alluded to above, output signal 706 is nonetheless driven back to the high state when an extension telephone device goes off hook while the modem remains off hook.
More particularly, if the modem is off hook but all other extensions on the same telephone line are on hook, the modem will aenerall~ draw a substantially constant current, for example on the order of 30 milliamps. If an extension telephone device then goes off hook, the combined current drawn by both telephone devices will be approximately equal to twice the current drawn by either device, but in reality will likely be slightly less than 60 microamps. This is analogous to the phenomenon one experiences when taking a shower in a home, whereupon a family member turns on the water in the sink located in the same bathroom as the shower. Although the water supply pressure (analogous to voltage) remains substantially constant, and further although the amount of water coming out of the shower head (analogous to modem current) is not adjusted, when the water in, the sink is turned on (analogous to an extension telephone device going off hook), the person taking a shower will typically notice a slight reduction in the rate of flow of the shower water.
Thus, although perhaps counter-intuitive, when an extension goes off hook while the modem is off hook, the current level drawn by the modem actually goes down slightly;
this reduction in current drawn by the modem causes opto-element 704 to cease activation, thereby sending output signal 706 back high. When the output signal 706 goes back high, as shown in Figure 8, this is detected by event detector circuit 218.
In accordance with a preferred embodiment of the present invention, extension on/off remote hangup detector circuit 218, upon detecting the return of output signal' 706 to the high state, can effectively discriminate between: (i) output signal 706 returning to the high state as a result of the modem going off=hook; and (ii) output signal 706 going back to the high state as a result of an extension telephone device going off hook. In accordance with a particularly preferred embodiment of the present invention, extension detection circuit 218 may effectively discriminate between the aforementioned conditions based on, for example, an output signal generated from relay circuit 214 which affirmatively indicates whether the modem is on hook or off hook. in particular, if output signal 706 returns to the high state and the modem remains off hook, DAA 202 may suitably conclude that _-. _. ___ AMEfVDED SHEET
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_. . , ~ n n , n o n o 0 0 o c, <9 r the return of signal 706 to the high state resulted from on extension.,~~epl~Piie deviF:P goi~lg"off hoo': n ~ ' If, on the other hand, signal 706 returns to the high state and it is determined that off hook relay circuit 214 was recently opened, DAA 202 may suitably conclude that the return of signal 706 to the high state resulted from the modem going back on hook as opposed to resulting from an extension telephone S device going off hook.
cr~rdarrc- _ ~~~L~rr--aspeet , circuit 218 is also suitably configured to detect a remote hangup condition, i.e., when the telephone device initiating an incoming call hangs up. More particularly, when the remote telephone device hangs up, the CO typically interrupts the DC component of the incoming signal for a brief period, for example on the order of 180 to 200 milliseconds. During this brief window of a DC null condition, the current loop line 222 goes idle. This idle condition may be suitably detected by LCS circuit 217, for example as described above. When a change in state in the output of LCS
circuit 217 is effected as a result of a remote hangup event, detector circuit 218 may be suitably configured to discriminate among the various possible causes of a change in state of the output signal produced by LCS circuit More particularly, a change in state of the output of LCS circuit 217 coula be caused by the DC
null occasioned by a remote hangup, an extension off hook condition while the modem is off hook, or a return of an off hook modem to the on hook condition, as discussed above. By tracking the state of the modem (i.e., either on hook or ofFhook) and of the off hook/on hook condition of extension telephone devices, DAA 202 may suitably infer whether a change in state of the output of LCS 217 is attributable to a remote hangup or, alternatively, to another event.
In accordance' with an alternate embodiment, remote hangup detector circuit 218 may also be configured to detect a remote hangup condition by detecting the presence of a DC null condition in current loop 222 for an anticipated window in the range of 180 to 200 milliseconds: This may be conveniently implemented in various ways using software, for example using a counter or other convenient technique. In addition, detector circuit 218 may be co~gured to detect the DC null .
condition via a hardware implementation, for example by detecting a low voltage condition (corresponding to the DC null interval), and thereafte>: a return to a higher relative voltage:condition upon termination of the DC null condition. '~
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" In yet a further embodiment, detector circuit 21 ~ may be co~fyu~ed io detcca, i r~rxodte hangup , condition by detecting a reversal in the polarity of the V«. That is, many COs signal a remote hangup by reversing the tip-to-ring polarity, either in lieu of or in addition to a brief cessation of the DC signal.
In this case, detector circuit 218 may be suitably configured to search for a polarity reversal, for example by detecting a zero crossing of the DC voltage in current loop 222.
'~b~Zlzil~e theTrP~ent ;nvention has been described with reference to certain preferred embodiments it will be appreciated, that various substitutions, changes, modifications, omissions, and enhancements in the invention may be made. For example, the circuit elements shown in the Figures are illustrative of the invention, but those skilled in the art will appreciate that the functionality described herein may be implemented in virtually any convenient manner. Accordingly, it is intended that the scope of the present invention not be limited by such a description but be fully coextensive with the broadest interpretation allowable for the appended claims.
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FULL FEATURED DATA A: CFlSS ARF.AN~EMEN~ ' ~ "
FOR USE WITH MODEMS
Inventor: Jeffrey Lee .a The present inventio=. relates, generally, to data access arrangement (DAA) devices, sometimes referred to as direct access arrangement devices, for connecting a telephone device to a telephone network and, more particularly, to a full-featured DAA configured to support evolving telephony industry standards.
Background Art and Technical Problems The Telecommunications Industry Association (TIA) and the Electronics Industry Association (EIA) from time to time promulgate non-binding technical standards for equipment sold in the telecommunications industry. While compliance with these standards by product manufacturers is generally voluntary, the practical importance of producing equipment in compliance with TIA/EIA standards is becoming increasingly important. In addition, the Federal Communication Commission (FCC) from time to time publishes binding regulations governing the telecommunications industry to ensure safety, compatibility, and to minimize problematic - interference among various electrical devices and components sold in the telecommunications industry.
In particular, Part 68 of the FCC Guidelines relates to such matters as, for example, the requirement that telephones and other telephone devices be electrically isolated from the telephone network to prevent shock, fire, and other environmental hazards from effecting the users of such equipment. In this context, the term "telephone device" can refer to telephones, modems, personal computers (PCS), fax machines, telephone answering machines (TAM), and the like, which are typically connected to a telephone line through a conventional RJ-11 telephone jack.
Recently, TIA/EIA Standards Proposal No. 3131-A was approved and published as TIA/EIA-695 which relates to, inter alia, various functions to be supported by data access arrangement (DAA) devices, also commonly referred to as direct access arrangement devices. In -~- particular, a DAA is a device which connects a telephone device, e.g., a modem, to an RJ-11 type _..
-.:r=
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_ __ ___ _ ' 20944.0516 < ,., r. r r ., I~ n cr ~~ _. ~ cr o ~ r r, ,. , .. ~. r r. n n ~ ~ n n r c: f n n t, .. n r, r c' c' ~. , .. ., jack, to thereby provide an interface between the m~demand tl~,laub~ie Switc'~r~ Telephone I~etwork~ -(PSTN). The DAA suitably includes an appropriate opto-electric or other isolation device to isolate the PSTN (which typically operates in the range of 42-200 volts) from the modem (which typically operates in the range of about 1 to 3 volts peak to peak). The transformer circuit within the DAA
which performs this voltage step-down function is often referred to as the primary transformer, or One of the principle functions of a conventional DA_A surrounds the ability of the DAA to w detect an incoming ring signal. When a ring signal is detected in a conventional telephone handset, the user can simply lift the telephone handset from the receiver, whereupon the telephone is said to go "off hook". Upon assuming the off hook position, the "off hook" relay within the DAA closes, thereby establishing a connection between the telephone handset and the telephone device which generated the incoming call. When the telephone call is finished and the user places the handset back onto the receiver, the handset is said to go back on hook, whereupon the off hook relay with?.n the DAA is open, terminating the connection.
In a modem context, upon detection of a ring signal, the DAA may be configured to transmit a ring detect signal to a controller associated with the modem or with the PC
with which the modem is associated, whereupon a control signal is applied to the DAA's off hook relay, closing the relay.
Upon closure of the off hook relay, a data communications path is established between the modem and the telephone device which generated the incoming call.
Many modems in use today, particularly modems associated with PCS, also include a local handset connection, such that both the data modem and the telephone handset are connected to the telephone network through a single, shared RJ-11 phone jack or other interface device. In this context, it will be understood that the term "telephone handset" can include audio speakers, a headset, a voice activated speaker phone, a condenser microphone, or virtually any other audio configuration which permits voice or audio transmission. Moreover, it will also be understood in the context of the present invention that the term "local handset" or "local device" refers to a telephone or other device which shares a common RJ-11 type device with a modem, whereas the term "extension handset" or "extension device" refers to a telephone device which is connected to a common telephone line (for ' 20944:0516 ' ' . , c ~. ~ , ..
n r .. r. n ~ n t? ' ,, C r.. n example, in another bedroom of the same home) bud which has its own-IFJ-11 type phone jack (:.~~, tho. ' extension telephone device does not share a common RJ-11 connection).
DAAs for use with a modem having a local handset are generally well-known, for example as described in Chapter 6 of the "K-Series Design Manual" published by Silicon Systems. Presently known DAAs, however, are unsatisfactory in several regards. For example, while a presently known ass cia -modem is off hook, many known DAAs are unable to detect an extension device off hook condition while the modem is on hook. Moreover, to the extent a presently known DAA is able to detect when an extension device goes off hook while the modem associated with the DAA is on hook under certain circumstances, the DAA is unable to ascertain when the extension device goes back on hook. One such DAA is disclosed in PCT application WO-A-95 14 344. In that application a telephone line monitoring circuit~for a modem monitors the tip and ring lines of the telephone line. A
first circuit detects when a local phone (extention phone as that term is used in the present appliction) goes off hook while the modem is on-hook by sensing a decrease in a differential voltage between the tip and ring lines. A
second circuit detects the pick up of a local phone while the modem is off hook by detecting a change in the impedance between the tip and ring lines. A third circuit detects the hang up of a remote phone connected with the modem while the modem is off=hook by detecting a temporary break in the DC
loop between the central office and the modem. The application does not disclose a circuit that detects whEn the local phone returns on-hook, either when the modem is on-hook or off hook.
A full featured DAA which overcomes the shortcomings of the prior art is thus needed.
The present invention provides a full-featured DAA for use with a modem which overcomes many of the shortcomings of the prior art.
Summar~of the Invention The present invention provides methods and apparatus for interfacing a phone device with a telephone network in a manner which overcomes many of the shortcomings of the prior art.
In accordance with a preferred embodiment of the present invention, a DAA
circuit is provided which detects when an extension telephone device goes off hook while the modem associated with the DAA is on hook, as well as detecting when the extension device goes back on hook. The ability of the ~
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subject DAA to detect when an extension device goes bask on hook is~paiticulara;z irrige'riant, ina.~muc~?~1., "
as it permits a facsimile or other data packet which is desired to be transmitted to be queued and transmitted from the queue once the extension telephone device goes back on hook.
In accordance with a further aspect of the present invention, when the modem with which the DAA is associated is in the off hook condition, the DAA is configured to detect when an extension the PC to which the modem is associated. In this way, the user can be informed that the modem connection has been terminated because of an extension off hook condition, as opposed to other common causes for modem disconnections, including Internet service provider (ISP) failure, line failure, local hard drive failure, or the like.
In accordance with a further aspect of the present invention, when the modem is in the off hook condition, its associated DAA may be configured to detect when a remote telephone device (i.e., the telephone device from which an incoming telephone call has been placed) is hung up. This permits a modem, for example operating in the TAM mode, to terminate the connection when the remote telephone device hangs up, thus avoiding the familiar but annoying dial tone which is often inadvertently replayed by many TaM users when checking their telephone messages, as a result of the recording device associated with the answering machine commencing its recording sequence immediately before the calling party hangs up.
In accordance with a further aspect of the present invention, many of the foregoing functions may be conveniently implemented in software, thereby providing an efficient, low cost, TIA/EIA
compliant DAA useful with current and future generation modems, including but not limited to the new 56kbps modem technologies currently emerging, for example the new 56K
modem chip sets ' produced by Rockwell Semiconductor Systems of Newport Beach, California.
Brief Description of the Drawing Figu The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like numerals denote like elements, and:
w Figure 1 is a schematic block diagram of an exemplary DAA circuit interconnecting a modem hybrid circuit with an incoming telephone line;
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n o o c ~ r, n r. c c n ~ r, r, Figure 2 is a schematic, functional block diagram of amerhaaaed DAA~circui*_ illustratsxig ate, arrangement of voltage and current detection components which provides enhanced event detection functionality to a DAA;
Figure 3 is a schematic block diagram of a single telephone line having a plurality of telephone extensions;
Figure 5 is a schematic circuit diagram of an exemplary line in use detection circuit;
--~ Figure 6 is a graphical depiction of the output signal generated by the line in use circuit of Figure ~;
Figure 7 is a schematic diagram of an exemplary embodiment of a line current sense circuit;
and Figure 8 is a graphical representation of an exemplary output of the line current sense circuit shown in Figure 7.
Detailed Description of Preferred Exemplary Embodiments Referring now to Figure 1, a conventional DAA 10 suitably connects a modem 12 to the Public Switched Telephone Network (PSTN), Private Branch Exchange (PBX), or the like.
As is known in the art, the incoming signal from the PSTN/PBX is typically carried on a pair of "wires" referred to as the tip and ring lines 18 and 20; respectively. TI=us, the tip-to-ring voltage is typically expressed as V tr. -Modem 12 suitably comprises a modem hybrid 14 and a voice hybrid 16 to facilitate the transmission of both voice and data through the same modem 12. Although modem hybrid 14 and voice hybrid 16 are illustrated schematically in Figure 1 as separate functional units, those skilled in the art will appreciate that the data and voice functions of modem 12 may suitably be integrated in any desired manner.
With continued reference to Figure 1, a preferred embodiment of the present invention is - suitably implemented in the context of a modem which includes a modem (or data) hybrid~component -and a voice hybrid component, such that the single modem can support data, facsimile; and other non-voice transmissions through incoming lines 18 and 20, as well as voice and other audio transmission 20944.0516 ~ ' n ~., ., .. _ . o ., . .
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' through voice lines 22 associated with a local hand set 16. In ~Li:s c~rtext, if wili be. ~zndersto~d that local handset 36 is connected to the PSTN through an RJ-11 type connector which the handset shares with DAA 10: In accordance with a particularly preferred embodiment, it will be appreciated that both voice and data is suitably transmitted to and from the PSTN through tip and ring wires 18 and 20.
More particularly, a voice relay circuit 24 is suitably configured to permit either the (simultaneous voice and data) function associated with conventional modems or, alternatively, voice relay 24 may be-configured to permit a transmission of data only or voice only.
With continued reference to Figure 1, a ring detect circuit 28 is suitably configured to detect the presence of an incoming "call" through the PST'N from a remote telephone device, i.e., a remote modem, fax machine, telephone handset, or the like. When an incoming call is detected, ring detect circuit 28 suitably sends a signal to modem 12, whereupon a signal may be applied to off hook relay 26 to thereby close the relay and accept the call. Once the call is accepted, the incoming AC signal is applied to modem 12, and a DC component of the incoming signal is transmitted through bridge circuit 30 to a DC current sink circuit 32. During a call connection, DC
current sink 32 suitably consumes a DC component of the incoming signal sufficient in magnitude to permit the detection of the call connection by the local exchange carrier (LEC) or the local Central Office (CO). When the -_ call is terminated, i.e., when off hook relay circuit 26 is again opened, the DC component transmitted through bridge circuit 30 is essentially terrlinated, allowing the CO to detect the completion of the call.
With continued reference to Figure 1, an event detection circuit 34 is suitably employed to monitor the magnitude of the loop current in DC current sink circuit 32, to thereby detect an off hook condition of an extension telephone device (e.g., by detecting a change in the loop current as a result of an extension off hook condition).
With continued reference to Figure 1, many conventional DAAs are configured such that off hook relay circuit 26 is in series with the incoming telephone line, as shown in Figure 1, as opposed to locating the off hook relay within the current sink loop connected to bridge 30. Consequently, for those DAAs wherein the off hook relay circuit is located in the incoming telephone line as shown in Figure 1, the DAA is typically only capable of detecting an extension telephone off hook condition when the modem is in the off hook condition (i.e., when off hook relay 26 is closed). Stated another °~'. ~."r . .:__......_..~__. .. o . .. .. ....__._.._.._...
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W~~Ww CA 02288608 1999-11-08 20944.0516 ;O . 0 0 n n .~ ,.. . , , r, ;. .
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i o , ..0 0 0 . r~ " ,. r. r, p c, ~ ~ n o o r. i: r. ~ , ~ ::~~ nn, way, it is necessary to establish a modem connection as pree~i?ditec~ri to tlie~aliility~of the LaAA t~~ ' detect certain external events, such as the off hook condition of an extension device, a hang up .. :~ec~a~:~.'..- . .-. c condition of a remote telephone, or the like. Moreover, the configuration of the off hook relay as shown in Figure 1 generally precludes the DAA from detecting many of these important external events when the computer associated with the modem is off or if a modem connection does not exist.
._ , suitably includes a caller ID relay 208, a ring detect circuit 220, a bridge 210, a bridge current loop circuit 222, a line in use detection circuit 212, an off hook relay 214, a DC
current sink circuit 216, a loop current sense (LCS) circuit 217 and an extension/remote event detector circuit 218. In addition to performing many of the functions set forth in TIA/EIA-695, DAA 202 suitably supports many of the existing functions associated with conventional DAAs, such as isolating modem 204 and its associated local handset 224 from the high voltage environment of the PSTN.
-- , With continued reference to Figure 2, off hook relay 214 is suitably connected in series with , - current sink loop 222, as opposed to being disposed in series with the incoming tip and ring lines, as is the case with may prior art DAAs. This improvement has substantial implications, as discussed in greater detail below, in that it permits DAA 202 to detect various external events even when a modem connection is not extant (i.e., even when off hook relay 214 is open).
With continued reference to Figure 2, those skilled in the art will appreciate that a caller ID
(CID) signal is generally transmitted from the LEC between the first and second audible rings. In accordance with a preferred embodiment of the present invention, ring detect circuit 220 is suitably configured to detect an incoming call, whereupon DAA 202 is advantageously configured to capture the telephone number or other indicia associated with the incoming call, via ring detect circuit 220, °
CID circuit 208, or through any other convenient mechanism. Once the ID of the incoming call is captured, it can be compared with a look up table stored in memory associated with the modem, or otherwise evaluated to determine whether the modem desires to accept the incoming call. For example, a list of destinations from which the modem desires to accept calls, or a list of destinations from which the modem desires to reject calls, or both, may suitably be compiled and stored in memory; for example in the form of a look up table. When the ID of the incoming call is captured arid compared to the look up table, the call may be accepted or rejected, as desired.
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If the call is to be accepted, the controller (ziot s'iown)<a~;;ocrated wits ~riodem°204 sen.:crs aa~~ °
appropriate signal to CID circuit 208, thereby closing the relay. The modem is also configured to transmit a signal to off hook relay circuit 214 to close the relay and thereby establish the call connection.
Once a call connection is established, bridge circuit 210 drops the line current, and converts a b 7 detectable by the Central Office (CO), such that the Cn can determine that the call connection has been made. The remaining AC component of the incoming signal is suitably applied to the modem hybrid circuit.
With continued reference to Figure 2, DC current sink circuit 216 suitably comprises a line current sense detector 217 for detecting an off hook condition of modem 204, while circuit 226 suitably comprises a loop current sense detector 227 for detecting an off hook condition of handset 224. In accordance with a particularly preferred embodiment, if during a modem connection the user desires to integrate voice into the transmission, the user may press a suitable function key or otherwise interact with the modem (or its associated PC), for example by depressing a predetermined key on the keyboard associated with the PC. In this way, the SVD function may be implemented, causing the voice relay circuit 228 to integrate the handset into the modem connection.
In accordance with a particularly preferred embodiment, when LCS circuit 226 detects the off hook condition of local handset 224, DAA 202 suitably signals the modem controller to initialize the SVD function.
In a particularly preferred embodiment, line in use circuit 212 is suitably implemented using a TMOS or other suitable, inexpensive electronic component. This is in contrast to prior art systems, which typically detect an off hook condition of an extension telephone device using a comparator circuit. By integrating the TMOS circuit into line in use detection circuit 212, the need for a-comparator circuit and its associated high cost is also eliminated. Moreover, the use of a TMOS or similar device draws very little current, for example on the order of 5 microamps, which further .
facilitates compliance with FCC Part 68. -In accordance with an alternate embodiment of the present invention, the subject LAA maybe °' configured to detect an off hook condition of an extension telephone device even when the modem hME~~~DEa SHcE!' 20944.0516 ~ ' ' ' a ~ nn ;,~ u~:
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remains off hook. Referring now to Figure 3, an i icorriing call~froin, tie Centc~r0f~ce (CO) X02 ia, suitably applied to a single telephone line 304 associated with a home, small office, or the like. In the illustrated. embodiment, the single phone line 304 suitably has associated therewith a plurality of extensions, for example a first extension 306 located in a bedroom, a second extension 308 located in the kitchen, and a third extension 310 which is suitably dedicated to a PC
having a local handset 312 , RJ-11 connection to the telephone line 304. When both the local modem and local handset associated with extension 310 are in the on hook condition, conventional DAAs associated with the modem at extension 310 are typically incapable of detecting an off hook condition of an extension handset, for example, in the kitchen. In order to detect an off hook condition on an extension telephone device while the local modem and local modem handset remain on hook, it may be desirable to incorporate a voltage detector circuit, for example as shown in Figure 4, to detect a reduction in voltage (or current) as a result of an extension off hook condition. More particularly, an extension off hook detector circuit 404 suitably comprises a storage capacitor 406 corresponding to an analog memory component, a detector circuit 408 having an output signal 410 associated therewith, and suitably configured to detect the tip-to-ring voltage associated with telephone line 304, which voltage is known to drop upon the occurrence of an off hook condition of any extension telephone device. However, it will be appreciated that sensing circuits such as that shown in Figure 4 are not readily capable of detecting when the extension telephone device goes back on hook and, hence, such circuits are of limited utility.
Returning now to Figures 2 and 5-8, a number of particularly preferred embodiments of the present invention suitably provide apparatus and techniques for detecting an off hook condition of an extension telephone device, as well as the return of that device to an on hook condition, regardless of whether the modem associated with the DAA is on hook or off hook.
With reference now to Figures 2 and 5-6, line in use detection circuit 212 is suitably co~gured to detect tip-to-ring voltage (or a scaled component thereof), for example within current loop 222. Line in use circuit 212 is also co~gured to generate an output signal 510 which, in the illustrated embodiment, is essentially a binary oa~put signal. Output signal 510 is suitably applied to the modem _ 20544.0516 ' ' ' ' n ;, .. ,.. , o n . . ~ 1 c. ,~
n . ~ n , ~ tv " , r' ~ o o , ~ ~ r controller (not shown) to indicate to the controller v!~ether the line r,s i~.
use, i. e: ,.vrhefber any exterisior~.
device is off hook, as described in greater detail below.
With continued reference to Figures 2 and 5-6, circuit 212 suitably comprises respective first and second resistors R1 and R2, respective first and second switches SW1 and SW2, respective current paths 504 and 506, and an opto-isolator element 502. It should be appreciated that the values of a wide variety of telephones, telephone lines, and telephone systems (i.e., PBX, PSTN, public telephones, and the like) to effect a change in output signal 510 upon a drop in tip-to-ring voltage Vtr.
With specific reference to Figures 5 and 6, output signal 510 applied to the modem controller is suitably high when no extension devices are in the off hook condition, whereas output signal 510 i~ suitably low when any extension (e.g., extension 306 or 308 in Figure 3) is in the off hook condition. In contrast to the voltage detection circuit illustrated schematically in Figure 4, the line in use detection circuit 212 shown in Figure 5 follows Vø in essentially real time, i.e., without the delay occasioned by capacitor 406. When no extensions are off hook, V« is high, such that SW1 is closed, causing current to flow through path 504. As a result, S W2 remains open, such that no current flows W rough path 506. With no current flowing through path 506, the opto-element 502 remains disabled, such that output signal 510 is pulled high. When an extension telephone device goes off hook, causing a drop in Vtr, SW1 opens, terminating the current flow through path 504. As a result, SW2 closes, producing current flow through path 506. The current flow activates opto-element 502, energizing the LED associated with the opto-element, such that output signal 510 is driven low. This phenomena is graphically illustrated in Figure 6, where time t~ corresponds to an extension telephone device going off hook, and the interval between times t, and t2 corresponds to the period in which an extension telephone device remains off hook.
In this way, the subject DAA set forth in Figure 2 and as explained above in conjunction with Figure 5 is capable of communicating to the modem controller a signal (signal 510) any time an extension telephone device goes off hook; while modem 204 is on hook.
Moreover, it will be appreciated that when the modem is off hook, i.e., during;a modem connection, the modem connection is typically terminateu when an extension telephone device goes off hook. This is analogous to a situation where a user of a PC (i, e., PC 310 in Figure 3) is involved in an online session (e.g., with an _ -10 _ _ ._ _ .. _ ._ . .._ _.
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r: .7 .C C c .i ~~ n p i :.n external ISP), and during the modem session, sorleor?e else .i~~tfi~ (louse 'u~vi~it~l.~Qiy picks.up ~, telephone in the kitchen (extension 308) or in the bedroom (extension 306). As a result, the modem connection is typically terminated, as distinguished from the situation where handset 312 may go off hook without terminating the modem session inasmuch as handset 312 and modem 310 enjoy the same RJ-11 connection to the telephone line. Notwithstanding the fact that the modem session may be ~tel<minated~~hen an PxtPn~ion telep one set goes off hook it may nonetheless be desirable to detect ' the off hook condition of an extension telephone set during a modem connection, as described below in conjunction with Figure 7, so that the PC user may be apprised of the reason for the termination of his modem connection; that is, it may be desirable for the PC to signal the PC
operator that the connection is terminated because of an off hook condition at an extension, so that the PC operator does not erroneously presume that the connection was terminated because of an ISP
failure, hard drive failure, line failure, or some other reason.
Refernng now to Figure 7, the loop current sense (LCS) circuit 217 of current sink 216 is suitably employed to detect an extension off hook condition when the modem is off hook, i.e., during a modem connection. The loop current sense circuit 217 suitably comprises an opto-isolator element 704 configured ~o generate an output signal 706 indicative of the state of loop current sense detector circuit 217. More particularly, the output of opto-isolator 704 is suitably pulled high (i.e., pulled to V~~. Thus, when modem off hook relay 214 is open, i. e., when the modem is in the on hook condition, output signal 706 is suitably high: When the modem goes off hook, relay 214 closes, producing a current flow through the opto-isolator 704, thereby driving output signal 706 low. . With momentary reference to Figure 8, output signal 706 is suitably high prior to time t," i.
e., while the modem is on hook. When the modem goes off hook at time tA, output signal 706 drops, as described' above. If the modem thereafter stays off hook, it is desirable to detect when an extension telephone device goes off hook while the modem remains in the off hook condition.
With continued reference to Figures 2 and 7-8, time tB suitably corresponds to an extension telephone device going off hook while the modem remains off hook.
Surprisingly, output signal 706 goes back high, even though the modem remains off hook (i.e., even though relay 214 remains closed).
Of course, if the modem were to go back on hook, i.e., if relay 214 were to open, output signal 706 _._ -____.__.~. . ,qMFNDED SHEET
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would also go back to the high condition, inasmuch as the curs°.~it vc~;i?.ld stop ~:oW rg Through opto-device 704, thereby driving output signal 706 high.
As alluded to above, output signal 706 is nonetheless driven back to the high state when an extension telephone device goes off hook while the modem remains off hook.
More particularly, if the modem is off hook but all other extensions on the same telephone line are on hook, the modem will aenerall~ draw a substantially constant current, for example on the order of 30 milliamps. If an extension telephone device then goes off hook, the combined current drawn by both telephone devices will be approximately equal to twice the current drawn by either device, but in reality will likely be slightly less than 60 microamps. This is analogous to the phenomenon one experiences when taking a shower in a home, whereupon a family member turns on the water in the sink located in the same bathroom as the shower. Although the water supply pressure (analogous to voltage) remains substantially constant, and further although the amount of water coming out of the shower head (analogous to modem current) is not adjusted, when the water in, the sink is turned on (analogous to an extension telephone device going off hook), the person taking a shower will typically notice a slight reduction in the rate of flow of the shower water.
Thus, although perhaps counter-intuitive, when an extension goes off hook while the modem is off hook, the current level drawn by the modem actually goes down slightly;
this reduction in current drawn by the modem causes opto-element 704 to cease activation, thereby sending output signal 706 back high. When the output signal 706 goes back high, as shown in Figure 8, this is detected by event detector circuit 218.
In accordance with a preferred embodiment of the present invention, extension on/off remote hangup detector circuit 218, upon detecting the return of output signal' 706 to the high state, can effectively discriminate between: (i) output signal 706 returning to the high state as a result of the modem going off=hook; and (ii) output signal 706 going back to the high state as a result of an extension telephone device going off hook. In accordance with a particularly preferred embodiment of the present invention, extension detection circuit 218 may effectively discriminate between the aforementioned conditions based on, for example, an output signal generated from relay circuit 214 which affirmatively indicates whether the modem is on hook or off hook. in particular, if output signal 706 returns to the high state and the modem remains off hook, DAA 202 may suitably conclude that _-. _. ___ AMEfVDED SHEET
20944.0516 .. r n n n ._ n . . n, , ..
c ~ n o c. n " r, r~ ~ , 1 r, r. , n r, n n n n n n r, n r, ,~ r.: ~
_. . , ~ n n , n o n o 0 0 o c, <9 r the return of signal 706 to the high state resulted from on extension.,~~epl~Piie deviF:P goi~lg"off hoo': n ~ ' If, on the other hand, signal 706 returns to the high state and it is determined that off hook relay circuit 214 was recently opened, DAA 202 may suitably conclude that the return of signal 706 to the high state resulted from the modem going back on hook as opposed to resulting from an extension telephone S device going off hook.
cr~rdarrc- _ ~~~L~rr--aspeet , circuit 218 is also suitably configured to detect a remote hangup condition, i.e., when the telephone device initiating an incoming call hangs up. More particularly, when the remote telephone device hangs up, the CO typically interrupts the DC component of the incoming signal for a brief period, for example on the order of 180 to 200 milliseconds. During this brief window of a DC null condition, the current loop line 222 goes idle. This idle condition may be suitably detected by LCS circuit 217, for example as described above. When a change in state in the output of LCS
circuit 217 is effected as a result of a remote hangup event, detector circuit 218 may be suitably configured to discriminate among the various possible causes of a change in state of the output signal produced by LCS circuit More particularly, a change in state of the output of LCS circuit 217 coula be caused by the DC
null occasioned by a remote hangup, an extension off hook condition while the modem is off hook, or a return of an off hook modem to the on hook condition, as discussed above. By tracking the state of the modem (i.e., either on hook or ofFhook) and of the off hook/on hook condition of extension telephone devices, DAA 202 may suitably infer whether a change in state of the output of LCS 217 is attributable to a remote hangup or, alternatively, to another event.
In accordance' with an alternate embodiment, remote hangup detector circuit 218 may also be configured to detect a remote hangup condition by detecting the presence of a DC null condition in current loop 222 for an anticipated window in the range of 180 to 200 milliseconds: This may be conveniently implemented in various ways using software, for example using a counter or other convenient technique. In addition, detector circuit 218 may be co~gured to detect the DC null .
condition via a hardware implementation, for example by detecting a low voltage condition (corresponding to the DC null interval), and thereafte>: a return to a higher relative voltage:condition upon termination of the DC null condition. '~
-13- ,..
20944.0516 r i o !~ ~ . r~ n ~ .. , ~ ~ . ~ ~ r r. ..
r, .. r, r. r ' " ~ , , n r, r: r. , n n .. n c~ r~
" In yet a further embodiment, detector circuit 21 ~ may be co~fyu~ed io detcca, i r~rxodte hangup , condition by detecting a reversal in the polarity of the V«. That is, many COs signal a remote hangup by reversing the tip-to-ring polarity, either in lieu of or in addition to a brief cessation of the DC signal.
In this case, detector circuit 218 may be suitably configured to search for a polarity reversal, for example by detecting a zero crossing of the DC voltage in current loop 222.
'~b~Zlzil~e theTrP~ent ;nvention has been described with reference to certain preferred embodiments it will be appreciated, that various substitutions, changes, modifications, omissions, and enhancements in the invention may be made. For example, the circuit elements shown in the Figures are illustrative of the invention, but those skilled in the art will appreciate that the functionality described herein may be implemented in virtually any convenient manner. Accordingly, it is intended that the scope of the present invention not be limited by such a description but be fully coextensive with the broadest interpretation allowable for the appended claims.
Claims (13)
1. A data access arrangement (DAA) device for interfacing a modem with an incoming telephone line of the type including a tip node and a ring node having a tip-to-ring voltage, V tr, imposed thereacross, and having circuits for detecting when an extention device (306, 308) coupled to said incoming telephone line goes off hook with said modem on-hook or off-hook and for detecting the hang up of a remote phone, said DAA device further characterized by:
a ring detection circuit (220) configured to detect V tr;
a bridge circuit (210) interposed between said ring node and said tip node, said bridge circuit being configured to extract a DC component from an incoming signal applied to said incoming telephone line and to apply said DC component to a current loop circuit (222) coupled to said bridge circuit;
a line in use detection circuit (212) coupled to said bridge circuit and configured to detect said DC component and to output a signal (510) having a first logic state if an extension device (306, 308) coupled to said telephone line is on-hook and a second logic state if said extension device is off-hook.
a ring detection circuit (220) configured to detect V tr;
a bridge circuit (210) interposed between said ring node and said tip node, said bridge circuit being configured to extract a DC component from an incoming signal applied to said incoming telephone line and to apply said DC component to a current loop circuit (222) coupled to said bridge circuit;
a line in use detection circuit (212) coupled to said bridge circuit and configured to detect said DC component and to output a signal (510) having a first logic state if an extension device (306, 308) coupled to said telephone line is on-hook and a second logic state if said extension device is off-hook.
2. The data access arrangement (DAA) device of claim 1 wherein said ring detection circuit (220) is coupled across said tip node and said ring node.
3. The data access arrangement (DAA) device of claim 1 wherein said current loop circuit comprises a series connected off hook relay (214) indicating the on-hook/off hook status of said modem (204).
4. The data access arrangement (DAA) device of claim 3 wherein said line in use circuit (212) is coupled in parallel with said bridge circuit (210) and is operative when said off hook relay (214) is indicative of said modem (204) being in an on-hook state.
5. The data access arrangement (DAA) device of claim 4 wherein said line in use circuit (212) comprises: a voltage divider coupled across said bridge circuit (210) to receive said DC
component, an output of said divider circuit coupled to the input of a first switch device coupled in series with a load device to form a first current path (504); an output taken from a node between said first switch device and said load device applied to a second switch device in series with a second load device to form a second current path (506), and an opto-isolator coupled to a device in said second current loop.
component, an output of said divider circuit coupled to the input of a first switch device coupled in series with a load device to form a first current path (504); an output taken from a node between said first switch device and said load device applied to a second switch device in series with a second load device to form a second current path (506), and an opto-isolator coupled to a device in said second current loop.
6. The data access arrangement (DAA) device of claim 3 wherein said current loop circuit (222) further comprises a loop current sense circuit (217) in series with said off-hook relay (214); said loop current sense circuit (217) being configured to detect when said modem (204) is in an off-hook state.
7. The data access arrangement (DAA) device of claim 6 wherein said loop current sense circuit (217) comprises an opto-isolator (704) in series with said off hook relay (214), said opto-isolator (704) producing a first logic level when said modem (204) is in an off-hook state and a second logic level when said modem (204) is in an on-hook state.
8. The data access arrangement (DAA) device of claim 7 wherein said opto-isolator (704) produces said second logic level when said modem (204) is off hook and an extension device (306, 308) goes off-hook.
9. The data access arrangement (DAA) device of claim 8 further comprising an event detection circuit (218) having inputs from said off hook relay (214) and said loop current sense circuit (217), said event detection circuit (218) configured to discriminate between said second logic state being caused by said modem (204) going on-hook and said extension device (306, 308) going off-hook.
10. The data access arrangement (DAA) device of claim of claim 6 further comprising an event detection circuit (218) comprising means to detect a remote hangup condition by detecting a DC
null condition in said loop current circuit (222).
null condition in said loop current circuit (222).
11. The data access arrangement (DAA) device of claim 6 further comprising an event detection circuit (218) comprising means to detect a remote hangup condition by detecting a reversal of said tip-to-ring voltage.
12. The data access arrangement (DAA) device of claim 1 further comprising a relay (228) for coupling a local handset (224) to said tip and ring nodes.
13. The data access arrangement (DAA) device of claim 12 further comprising a second loop current sense detector (227) for detecting an off hook condition of said local handset (224).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/864,659 | 1997-05-28 | ||
| US08/864,659 US6005923A (en) | 1997-05-28 | 1997-05-28 | Full featured data access arrangement for use with modems |
| PCT/US1998/010613 WO1998054886A1 (en) | 1997-05-28 | 1998-05-26 | Full featured data access arrangement for use with modems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2288608A1 true CA2288608A1 (en) | 1998-12-03 |
Family
ID=25343769
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002288608A Abandoned CA2288608A1 (en) | 1997-05-28 | 1998-05-26 | Full featured data access arrangement for use with modems |
Country Status (10)
| Country | Link |
|---|---|
| US (2) | US6005923A (en) |
| EP (1) | EP0985311B1 (en) |
| JP (1) | JP3396225B2 (en) |
| KR (1) | KR100325777B1 (en) |
| CN (1) | CN1134966C (en) |
| AT (1) | ATE201121T1 (en) |
| CA (1) | CA2288608A1 (en) |
| DE (1) | DE69800772T2 (en) |
| HK (1) | HK1029239A1 (en) |
| WO (1) | WO1998054886A1 (en) |
Families Citing this family (43)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6222922B1 (en) | 1997-04-22 | 2001-04-24 | Silicon Laboratories, Inc. | Loop current monitor circuitry and method for a communication system |
| US6385235B1 (en) | 1997-04-22 | 2002-05-07 | Silicon Laboratories, Inc. | Direct digital access arrangement circuitry and method for connecting to phone lines |
| US6442271B1 (en) | 1997-04-22 | 2002-08-27 | Silicon Laboratories, Inc. | Digital isolation system with low power mode |
| US6498825B1 (en) | 1997-04-22 | 2002-12-24 | Silicon Laboratories Inc. | Digital access arrangement circuitry and method for connecting to phone lines having a DC holding circuit with programmable current limiting |
| US5870046A (en) | 1997-04-22 | 1999-02-09 | Silicon Laboratories Inc. | Analog isolation system with digital communication across a capacitive barrier |
| US6389134B1 (en) | 1997-04-22 | 2002-05-14 | Silicon Laboratories, Inc. | Call progress monitor circuitry and method for a communication system |
| US6298133B1 (en) * | 1997-04-22 | 2001-10-02 | Silicon Laboratories, Inc. | Telephone line interface architecture using ringer inputs for caller ID data |
| US6144326A (en) | 1997-04-22 | 2000-11-07 | Silicon Laboratories, Inc. | Digital isolation system with ADC offset calibration |
| US6289070B1 (en) | 1997-04-22 | 2001-09-11 | Silicon Laboratories, Inc. | Digital isolation system with ADC offset calibration including coarse offset |
| US6442213B1 (en) | 1997-04-22 | 2002-08-27 | Silicon Laboratories Inc. | Digital isolation system with hybrid circuit in ADC calibration loop |
| US6480602B1 (en) | 1997-04-22 | 2002-11-12 | Silicon Laboratories, Inc. | Ring-detect interface circuitry and method for a communication system |
| US6504864B1 (en) | 1997-04-22 | 2003-01-07 | Silicon Laboratories Inc. | Digital access arrangement circuitry and method for connecting to phone lines having a second order DC holding circuit |
| US6167134A (en) * | 1997-04-22 | 2000-12-26 | Silicon Laboratories, Inc. | External resistor and method to minimize power dissipation in DC holding circuitry for a communication system |
| US6167132A (en) * | 1997-04-22 | 2000-12-26 | Silicon Laboratories, Inc. | Analog successive approximation (SAR) analog-to-digital converter (ADC) |
| US6587560B1 (en) | 1997-04-22 | 2003-07-01 | Silicon Laboratories Inc. | Low voltage circuits powered by the phone line |
| US6516024B1 (en) | 1997-04-22 | 2003-02-04 | Silicon Laboratories Inc. | Digital access arrangement circuitry and method for connecting to phone lines having a DC holding circuit with low distortion and current limiting |
| US6307891B1 (en) | 1997-04-22 | 2001-10-23 | Silicon Laboratories, Inc. | Method and apparatus for freezing a communication link during a disruptive event |
| US6408034B1 (en) | 1997-04-22 | 2002-06-18 | Silicon Laboratories, Inc. | Framed delta sigma data with unlikely delta sigma data patterns |
| US6359983B1 (en) | 1997-04-22 | 2002-03-19 | Silicon Laboratories, Inc. | Digital isolation system with data scrambling |
| US6160885A (en) * | 1997-04-22 | 2000-12-12 | Silicon Laboratories, Inc. | Caller ID circuit powered through hookswitch devices |
| US6456712B1 (en) | 1997-04-22 | 2002-09-24 | Silicon Laboratories Inc. | Separation of ring detection functions across isolation barrier for minimum power |
| US6137827A (en) | 1997-04-22 | 2000-10-24 | Silicon Laboratories, Inc. | Isolation system with digital communication across a capacitive barrier |
| US6724891B1 (en) | 1998-03-04 | 2004-04-20 | Silicon Laboratories Inc. | Integrated modem and line-isolation circuitry and associated method powering caller ID circuitry with power provided across an isolation barrier |
| US6714590B1 (en) * | 1999-07-23 | 2004-03-30 | Silicon Laboratories, Inc. | Integrated modem and line-isolation circuitry and associated method |
| US6711160B2 (en) * | 1998-03-31 | 2004-03-23 | International Business Machines Corporation | Packet network telephone interface system for POTS |
| US6744888B1 (en) * | 1998-11-16 | 2004-06-01 | Agere Systems Inc. | Line interface circuit with event detection signaling |
| US6826225B1 (en) | 1999-07-23 | 2004-11-30 | Silicon Laboratories, Inc. | Integrated modem and line-isolation circuitry with selective raw data or modem data communication and associated method |
| US6735246B1 (en) | 1999-07-23 | 2004-05-11 | Silicon Laboratories Inc. | Integrated modem and line-isolation circuitry with data flow control and associated method |
| US6662238B1 (en) | 1999-07-23 | 2003-12-09 | Silicon Laboratories Inc. | Integrated modem and line-isolation circuitry with command mode and data mode control and associated method |
| US7020187B1 (en) | 1999-07-23 | 2006-03-28 | Silicon Laboratories Inc. | Integrated modem and line-isolation circuitry with HDLC framing and associated method |
| US6700974B1 (en) * | 1999-09-16 | 2004-03-02 | Conexant Systems, Inc. | Switching power supply for generating a ringing voltage |
| US6442248B1 (en) * | 2000-01-12 | 2002-08-27 | Multi-Tech Systems, Inc. | System for providing analog and digital telephone functions using a single telephone line |
| US7227933B1 (en) | 2000-01-12 | 2007-06-05 | Multi-Tech Systems, Inc. | System and method for remote management of a DSL device |
| FR2808396B1 (en) | 2000-04-27 | 2003-01-31 | St Microelectronics Sa | SOCKET DETECTION CIRCUIT |
| US7127209B2 (en) * | 2001-04-27 | 2006-10-24 | Agere Systems Inc. | Method and system for providing accurate service record using phone line detector |
| US6687344B1 (en) | 2001-09-07 | 2004-02-03 | Pctel,Inx. | Parallel handset on-hook/off-hook detection by software-based signal power measurement |
| JP3961934B2 (en) * | 2001-12-20 | 2007-08-22 | 株式会社リコー | Facsimile device |
| US7277491B2 (en) * | 2002-05-14 | 2007-10-02 | Ess Technology, Inc. | Data access arrangement using a high frequency transformer for electrical isolation |
| KR100484169B1 (en) * | 2002-10-17 | 2005-04-19 | 삼성전자주식회사 | Communication apparatus and that using method |
| US7218713B1 (en) | 2003-04-15 | 2007-05-15 | Silicon Laboratories Inc. | Telephone line interface for DAA circuitry |
| JP4192856B2 (en) * | 2004-07-07 | 2008-12-10 | ブラザー工業株式会社 | Communication device, line closing method and program |
| US20070121923A1 (en) * | 2005-09-15 | 2007-05-31 | Tyco Safety Products Canada, Ltd. | Telephone line communication interface |
| US7835516B2 (en) * | 2005-12-29 | 2010-11-16 | Tyco Safety Products Canada Ltd. | Direct access arrangement device |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4640988A (en) * | 1984-04-03 | 1987-02-03 | Robinton Products, Inc. | Telephone interrupter |
| US5291545A (en) * | 1990-10-02 | 1994-03-01 | Intertex Data Ab | Apparatus and method for determining the state of a telephone line |
| US5506891A (en) * | 1993-07-06 | 1996-04-09 | Cirrus Logic, Inc. | Method and apparatus for detecting the connection status of an extension phone connected to a voice/fax/data modem |
| US5422939A (en) * | 1993-08-05 | 1995-06-06 | Schlumberger Industries, Inc. | Parallel off-hook detection for both line-available and phone pick-up detection |
| US5535265A (en) * | 1993-11-15 | 1996-07-09 | Ast Research, Inc. | Method and circuitry for controlling voice mail, call logging and call blocking functions using a modem |
| US5519767A (en) * | 1995-07-20 | 1996-05-21 | At&T Corp. | Voice-and-data modem call-waiting |
| US6134321A (en) * | 1995-12-22 | 2000-10-17 | Thomas Licensing S.A. | Modem loop current detect system to detect an off-hook condition in an extension telephone |
| US5867560A (en) * | 1996-05-24 | 1999-02-02 | Rockwell International Corporation | Remote hang-up detector |
-
1997
- 1997-05-28 US US08/864,659 patent/US6005923A/en not_active Expired - Lifetime
-
1998
- 1998-05-26 WO PCT/US1998/010613 patent/WO1998054886A1/en active IP Right Grant
- 1998-05-26 CN CNB988055309A patent/CN1134966C/en not_active Expired - Fee Related
- 1998-05-26 JP JP50079499A patent/JP3396225B2/en not_active Expired - Fee Related
- 1998-05-26 DE DE69800772T patent/DE69800772T2/en not_active Expired - Fee Related
- 1998-05-26 CA CA002288608A patent/CA2288608A1/en not_active Abandoned
- 1998-05-26 AT AT98923731T patent/ATE201121T1/en not_active IP Right Cessation
- 1998-05-26 EP EP98923731A patent/EP0985311B1/en not_active Expired - Lifetime
- 1998-05-26 KR KR1019997010914A patent/KR100325777B1/en not_active IP Right Cessation
-
1999
- 1999-07-01 US US09/346,248 patent/US6456703B1/en not_active Expired - Fee Related
-
2000
- 2000-09-15 HK HK00105812A patent/HK1029239A1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| CN1134966C (en) | 2004-01-14 |
| DE69800772T2 (en) | 2001-11-29 |
| CN1258410A (en) | 2000-06-28 |
| ATE201121T1 (en) | 2001-05-15 |
| KR20010012944A (en) | 2001-02-26 |
| DE69800772D1 (en) | 2001-06-13 |
| JP2000513186A (en) | 2000-10-03 |
| US6005923A (en) | 1999-12-21 |
| EP0985311A1 (en) | 2000-03-15 |
| WO1998054886A1 (en) | 1998-12-03 |
| KR100325777B1 (en) | 2002-03-06 |
| US6456703B1 (en) | 2002-09-24 |
| HK1029239A1 (en) | 2001-03-23 |
| JP3396225B2 (en) | 2003-04-14 |
| EP0985311B1 (en) | 2001-05-09 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Discontinued |