CA1254979A - Telephone paging system and method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An improved telephone paging system and method are disclosed. The system interfaces with a convention-al telephone branching system, such as a PBX, and remote pager devices which are worn by subscribers to the sys-tem. A plurality of PBX extension telephone lines are connected to the system via a subscriber line inter-face, and one PBX extension line is connected to this system via a control line interface. The subscriber line interface is used to detect ring signals on the selected extension lines. When a ring signal has been detected on a selected line, the microprocessor-based system sends command signals to the PBX to place the incoming call on hold. The system identifies a paging code signal distinctively corresponding to the subscriber line on which the ring signal was detected. The identi-fied paging code signal is sent to a transmitter which transmits the paging code signal to all pagers within its range. The pager which distinctively corresponds to the paging code signal will be activated and produce a paging signal. The subscriber may then retrieve the parked call from the PBX via any PBX extension line.
To perform these functions, the subscriber to the dis-closed telephone paging system may also enable or dis-able his pager, test his pager, or directly page another subscriber via the dedicated command line. To perform these functions, a subscriber calls the extension phone number corresponding to the command line and depresses the telephone keys which represent certain instruction in response to command signals sent by the microproces-sor. Other embodiments of the telephone paging system are disclosed that interface with a PBX with a directed-call-pickup feature and that permit additional extension lines to be connected to the system.

Description

~L~ 7~

TELEPHONE PAGING SYSTEM AND METHOD

BAC~GROUND OF THE I~ENTION

This invention generally relates to a tele-phone paglng system and method, and in particular to a system and method for transmitting paging signals based on calls directed to selected telephone extension lines.
It is not uncommon for people to be away from their telephones when they ring. If someone else is not present to pick up the call, an important message might be delayed or missed. And even if someone else does answer the phone, the message may still be delayed or missed if that person does not know the immediate whereabouts or how to contact the intended recipient.
A missed, or even delayed, important message can have severe consequences (e.g., if the intended recipient is a doctor).
One solution to this problem has been the development of the paging terminal system which sends signals to a person wearing a remote pager device that informs him that someone is trying to contact him.
When a person desires to contact a person subscribing to the paging terminal system (hereinafter "subscrib-er"), he calls a phone number corresponding to a cen-tral paging terminal. The particular phone number called may distinctively correspond to the particular pager worn by the intended subscriber, or the terminal . ~a~

-2~ 12~'~3 ~

may request the caller to enter a code distinctively corresponding to the subscriber. The paging terminal searches its data base to identify the particular sub-scriber corresponding to the number called or code num-ber entered, what type of pager he wears, and what sig-nals must be transmitted to activate the pager. A sig-nal which activates the pager of the identified sub-scriber is then transmitted to all pagers within its range.
Conventional pagers can respond in a variety of ways to the transmitted signal. For example, they can produce a repetitive tone signal (e.g., a "beep") which notifies the subscriber to call an answering ser-vice to learn the identity of the caller or hear a re-corded message, or they can produce an audio or visual signal containing the message that the subscriber can directly observe.
While this type of system informs a subscriber that someone is trying to contact him, it also has some drawbacks. For example, a caller may typically know the home or work phone numbers of the subscriber, which he may call first. If the subscriber is not present, the caller must know and remember the phone number of the subscriber's paging terminal and, possibly, an ad-ditional subscriber identification code. Thus, thecaller must go through a number of steps before a pag-ing signal is transmitted to the subscriber. Another drawback is that ~here is no interactive communication with the system after the subscriber receives the page.
If the subscriber wears one of the relatively unsophis~
ticated pagers -that only produces a repetitive tone, he must call his answering service to find out the message or the identity of the caller who must then be contacted.
Even if the subscriber wears a pager that transmits an audio or visual message, he must still contact the caller to clarify questions or to respond to the message.

-SUMMA~Y_OF THE INVENTION
The present invention is directed to an im-proved paging system and method which allows a person subscribing to the system to be paged via the subscrib-er's existing phone line.
According to this invention, a plurality of extension telephone lines of a conventional telephone line switching means (e.g., a PBX) are selected for connection to the paging sys~em. ~ detection means detects signals representing calls directed to the se-lected extension lines. A storing means contains a plurality of different paging code signals, wherein each paging code signal distinc~ively corresponds to one of the selected extension lines. An identification means identifies the paging codes signal corresponding to the selected extension line for which a call signal has been detected. A transmitting means is provided to transmit the identified paging code signal to a receiv-ing means that is responsi~e to that particular paging code signal.
In the presently preferred embodiment, the invention interfaces with a switching means that also has the capability to hold a call. A detection means is connected to each selected extension line to sense signals representing rings. When a ring signal is de-tected on a selected extension line, a control means sends a signal to the switching means to hold the call.
The identi~ication means identifies the stored paging code signal corresponding to the selected extension line on which a predetermined number of ring signals has been detected. The transmitting means transmits the identified paging code signal ~o a plurality of receiving means, one of which is responsive to the transmitted paging code signal.
Thus, in the preferred embodiment, when a predetermined number of ring signals is detected on a r ~t~3 selected extension line, a control signal is sent to the switching means to hold the call and a paging code signal corresponding to that extension line is trans-mitted to a receiving device which is responsive to the paging code signal. This object provides several ad-vantages. For example, a person subscribing to one of the selected extension lines can be directly paged by someone calling his regular telephone number. The caller does not have to remember a special paging terminal telephone number or an identification code for the sub-scriber. The invention also readily interfaces with a conventional telephone line switching means, thereby facilitating its implementation on an existing phone system and obviating the need for a separate paging terminal system. Further advantages are realized be-cause the call is placed on hold. The switching means used in the preferred embodiment allows a held call to be retrieved from any extension, thereby permitting the intended subscriber to retrieve the call after he is paged. This permits ~uick interactive communication with the caller.
The invention can also be interfaced with other types of conventional -telephone line switching means so that it can take advantage of some of the functions available on these switching means. For example, another embodiment of the invention interfaces with a switching means that permits a subscriber to pick up a call on an extension line from any other ex-tension line. The invention can be interfaced to this switching means to eliminate the control means which places a call on hold. A paging code signal would then be transmitted while allowing the phone to ring. Upon being paged, the subscriber could pick-up the call from any extension line.
Another feature of the preferred embodiment of the present invention is that one of the extension -5~

lines of the switching means can be selected for com-mand signals. A ring detection means and a code de-tec.ion means, which senses signals representing in-structions, are connected to the command line. The storing means contains command signals which correspond to a ring signal on the command line or to instruction signals and paging signals which also correspond to instruction signals. The identifying means identifies the command signal corresponding ~o a ring signal or an instruction signal on the command ].ine and the paging code signal corresponding to a subscriber line or an instruction. The control means sends the identified command signal to the switching means, and the trans-mitting means transmits identified paging code signals.
By using the command line and appropriate instruction signals, a subscriber can enable or disable his paging code signal or directly page another sub-scriber.
Although some preferred aspects of the invention have been referred to and others will become apparent herein, the invention in one broad aspect comprehends a telephone paging system comprising means for detecting telephone call signals switched from one telephone line to one or more telephone lines, and means for selecting and transmitting a stored paging code signal that distinctively corresponds to the telepho.ne line for which a call signal has been detected, each stored paging code signal being operative to activate one of a plurality of remote paging devices.
Another broad aspect of the invention comprehends a telephone paging system comprising means for detecting telephone call signals on a telephone line, means for de-tecting instruction signals on the telephone line, means for sending command signals over the telephone line when a t~

-5a-predetermined number of call signals or instruction signals have been detected on the telephone line, and means for selecting and sending a particular paging code signal to a remote paging unit via the telephone line in response to a predetermined instruction signal sent from another telephone line.
The invention also comprehends a telephone paging system comprising means for detecting a telephone call directed to one or more telephone lines, means for trans-mitting a paging code signal that distinctively correspondsto the telephone line for which a telephone call has been detected, the paging code signal being operative to activate a remote paging device. In one aspect means are provided for allowing the detected telephone call to be received at a telephone line other than the one upon which the telephone call has been detectedO
In another aspect means are provided for automati-cally holding telephone call signals while the transmitting means transmits a paging code signal, and means then allow held telephone call signals to be accessed from a telephone line other than the one for which the telephone call signals have been detected.
In a still further aspect means are provided for automatically sustaining a telephone call while the trans-mitting means transmits the paging code signal, and meansthen allow a sustained telephone call to be accessed from a telephone line other than the one for which the telephone call was detected.
A still further aspect pertains to a telephone system including branching means for switching signals on an incoming telephone line between a plurality of extension telephone lines and a plurality of means for receiving paging code signals, each receiving means being responsive to a particular paging code signal. The improvement comprises -5b-means for selecting a plurality of extension telephone lines, means for detecting signals directed to selected extension lines representing a cal]., means for storing a plurality of signals representing different paging codes, wherein each paging code signal distinctively corresponds to one of the selected extension li.nes and a receiving means, means for identifying the paging code signal corresponding to the selected extension line for which the detecting means detected a call signal, and means for transmitting the identified paging code signal to a plurality of the receiving means.
The invention also comprehends a telephone paging method comprising selecting a plurality of extension telephone lines on a branching means for switching signals on an incoming telephone line between a plurality of extension lines, detecting signals representing rings on the selected extension lines, parking a call on the branching means when a ring signal is detected on an extension line, storing a plurality of signals representing different paging codes, wherein each paging code signal distinctively corresponds to a selected extension li.ne, identifying the paging code signal corresponding to the selected extension line on which a predetermined number of ring signals has been detected, and transmitting the identified paging code signal to a plurality of means for producing paging signals in response to different paging code signals.
Still further, the invention comprehends a telephone paging method comprisiny selecting a plurality of extension telephone lines on a branching means for switching signals on an incoming telephone line between a plurality of extension lines, detecting signals representing calls to the selected extension lines, storing a plurality of signals representing different paging codes, wherein each paging code signal distinctively corresponds to a L7!~7 ~3 -5c-selected extension line, identifying the paging code signal corresponding to the selected extension line for which a call signal has been detected, and transmitting the identified paging code signal to a plurality of means for producing paging signals in response to different paging code signals.
Further aspects and advantages of the invention will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a block diagram of a telephone paging system including a preferred embodiment of the present invention.
FIGURE la is a circuit diagram of the trans-mitter level converter of the preferred embodiment of the present invention.
FIGURE lb is a circuit diagram of a voltage regulator used in the preferred embodiment of the present invention.
FIGURE 2 is a schematic view of the sub-scriber line interface of the preferred embodiment of the present invention.

FIGURE 3 is a schematic view of the command line interface of the preferred embodiment of the pre-sent invention.
FIGURE 4 is a schematic view of a subscriber line interface of another embodiment of the present invention.
FIGURE 5 is a schematic view of another em-bodiment of the present invention.

DETAILED DESCRIPTION OE PREFERRED EMBODIMENT
Referring now to the drawings, a preferred embodiment of the improved paging system and method of the present invention will be described in connection with the telephone paging system shown in FIGS. 1-3.
FIG. 1 shows the major components of a tele-phone paging system 10 which interfaces with a conven-tional PBX 11. The basic function of the PBX 11 is to provide the capability of switching signals on an in-coming telephone line 13 to any one of its extension lines 100-200. Thus, the PBX allows a large number of people subscribing (hereinafter "subscribers") to the various extension lines to be able to receive calls through relatively few incoming trunk lines 13. A typ-ical PBX also permits one subscriber to directly call another subscriber by dialing the latter's extension phone number.
A wide variety of PBXs are available with this switching function (also referred to as a branch-ing or demultiplexing function) as well as with various special functions. A General Dynamics PBX 11 (FCC Reg.
No. BJ885Z-6779-PF-E) is connected to the presently preferred embodiment of the invention. This PBX 11 places a call directed to one of the extension lines on hold or "park" when it receives a predetermined command signal on tha-t extension line. The subscriber trans-mits the appropriate command signal to the PBX 11 for _7_ ~ 7~

example, by quickly depressing and releasing the hook-lever on his phone and then entering a number from his telephone keypad that represents the call-parking func-tion. The PBX 11 also allows a subscriber to retrieve a parked call from any extension line connected to the PBX 11 by entering an appropriate instruction via the keypad on a push-button telephone.
There are 101 extension lines 100-200 con-nected to the PBX 11 as shown in FIG. 1. Thirty-one of these extension lines 101-131 are selected for connec-tion to the telephone paging system 10 via the subscri-ber line interfaces 36. A separate unused extension line 100 is selected for connection to the system via the control line interface 38. Thus, a total of 32 telephone extension lines are selected for connection to the system. The selected extension lines 101-131 which are connected to a subscriber line interface 36 will be referred to as subscriber lines, and the exten-sion line 100 connected to the control line interface 38 will be referred to as the dedicated control line or command line. The persons whose extension telephones are connected to the subscriber lines 101-131 will be referred to as subscribers. The persons trying to di-rect a telephone call to a subscriber will be referred to as callers.
The basic control of the telephone paging system 10 is provided by the CPU 12, which executes the computer progam contained in the program listing ap-pended hereto. The presently preferred embodiment uses a conventional Z-8~00 microprocessor for the CPU 12.
The CPU 12 as well as the memory 16, SIOs 18, output CTCs 30, event CTCs 32, and PIOs 34 are controlled by timing signals derived from a master clock signal pro-vided by the oscillator 14. The oscillator 14 used in the preferred embodiment is a Vectron C0231T-5, which produces a 19.6608 MHz master clock signal. This crystal frequency is preferred because it can be easily divided to provide the baud rates required by the SIOs 18. It is important that the clock signal provided by the oscillator 14 is stable for the paging formats to work correctly. The oscillator 14 divides the master clock frequency to several different frequencies which are output from different ports of the oscillator.
The memory 16 used in the presently preferred embodiment consists of two 2K x 8 RAMs (model no. TMS
4016) and up to eight 4K x 8 EPROMs (model no. 2732).
The RAM is used to store variables that may be entered by the user through a conventional video terminal key-board 19 (see FIG. 5) and program data variables that are used and updated during operation of the system.
The EPROM is used to hold the master data base and the operating program for the CPU 12. The operating pro-gram is run directly from the EPRO~.
The master data base record contains coded signals distinctively corresponding to each subscrib-er's extension telephone number, pager identificationnumber, status ~i.e. whether a subscriber's pager is enabled or disabled), and physical extension line num-ber (e.g., 101-131). The pager identification number is the paging code signal that is transmitted to activ-ate a subscriber's pager. A sample master data baserecord is included in the program listing appended hereto.
A copy of the master data base record is mapped into the RAM when the system 10 is initialized.
These data can then be modified by the user via the video terminal keyboard 19 or some other means. For example, a particular subscriber may initially want his pager to be disabled (i.e., not have paging signals transmitted when his phone rings) when the system 10 is initialized. The subscriber can subsequently directly enable his device by means which will be exp]ained below.

9 ~ 7~

In operation the CPU 12 uses the data base stored in RAM, which reflects the current status of the system and each subscriber.
The EPROM is used to store the master data base record and operating program to avoid re-loading that information whenever there is a power interrup-tion. As a further enhancement of the system 10, a conventional non-volatile memory could be used in place of the EPROM and RAM. This would obviate the need for the working copy of the data base presently stored in RAM.
Two conventional SIOs 18 (Zilog model no.
Z8440) are used to transmit paging code signals to a transmitter 25 and the video terminal display l9. A
conventional General Electric transmitter (part no.
l9D43296G1) is used to transmit paging code signals to the subscribers' pagers via a ground plane antenna 26.
The antenna 26 is made from wire in a standard ground plane configuration that provides omnidirectional sig-nals corresponding to the paging frequency of thetransmitter 25. A Qume QVTl02 video terminal 19 is used for monitoring the system, such as displaying sys-tem status, and providing a means for adding to or up dating the copy of the subscriber data base records stored in RAM.
One of the SIOs provides serial data communl-cation which is compatible with the transmitter 25, and one provides serial data communication which is compat-ible with the video terminal 19. The transmitter 25 requires a digital signal from the SIO 18 output at a 510 baud rate in accordance with the POCSAG paging for-mat. The video terminal l9 requires a digital signal from the SIO 18 output at a 2400 baud rate in accord-ance with the ASCII format.
Voltage level converters 20-23 are connected to the output lines of the SIOs 18 to translate output _g_ signal voltage levels to voltage levels that are com-patible with e~ternal peripheral devices (such as the video terminal 19). A conventional r~otorola MC1488 or MC1489 level converter may be used for the level con-verters 20-23. The video terminal 19 is interfaced directly to the level converter 0.
An additional transmitter level converter 24, shown in Fig. 1~, is connected between the level con-verter 23 and the transmitter 25. The pins 78, 79, 80 of the transmitter level converter 24 are connected to the outputs of the level converter 23 via a conven-tional 25-pin connector, and the pins 81, 82, 83, 84, 85 of the transmitter level converter 24 are connected to the transmitter 25 via a conventional 10 pin connec-tor. The CPU 12 sends a power-up signal to the connec-tor pin 78 via the SIOs 18 in advance of sending the paging code signal data to the connector pin 79. The transistor network 86 converts the voltage level of the power-up signal to the voltage level compatible the transmitter 25 and amplifies the current to the level required by the transmitter. The two potentiometers 87 and 88 adjust the voltage level of the paging code data signal so that it is compatible with the transmitter 25. Connector pins 80, 83, and 84 are tied to a common ground so that the transmitter 25 will have the same ground level as the other components of the telephone paging system 10.
Fig. lb shows the components of a voltage regulator circuit 89 that provides the bias voltage +V
to the transistor network 86, the potentiometer 88, and the transmitter 25 via connector pin 85. The output voltage +V is adjusted via the potentiometer 90 to pro-vide 10 volts. The particular voltage regulator 89 shown in Fig. lb is designed operate with low power dissipation.

~ 7 ~

Two conventional control counter-timer cir-cuits (CTC) 30 (Zilog model no. Z8430) are used to pro-vide the clock signals to the clock input ports of the SIOs 18. One CTC 30 provides a clock signal corre-sponding to the baud rate of signals sent to the videoterminal 19, and one provides a clock signal correspond-ing to the baud rate for signals sent to transmitter 25.
A conventional event CTC 32 (Ziolg model no Z8430) is provided to monitor real-time events. The event CTC 32 counts a predetermined number down to zero, whereupon an interrupt signal is sent to the CPU 12.
The interrupt tells the CPU 12 that a predetermined amount of time has elapsed since the last interrupt.
The CPU 12 is programmed to perform a predetermined operation in response to the interrupt signal.
In the preîerred embodiment, the CPU 12, upon receipt of an interrupt from the event CTC 30, reloads the CTC 30 so it can count down again. The CPU then updates a real-time clock which is stored in software.
The CPU 12 then scans each subscriber line interface 36 for detected ring signals. The CPU samples the ring signal on each successive interrupt to measure its duration. If the duration of the measured signal is longer or shorter than the duration of a standard ring signal, the CPU 12 knows the detected signal is not a valid ring signal. The event CTC 32 also may be adapted to schedule additional real-time events that a user may program into the operating program stored in the memory 16.
FIG. 1 also shows seven standard parallel input/output controllers (PIOs) 34 (Zilog model no.
Z8420) that connect all the subscriber line interfaces 36 and the command line interface 38 with -the CPU 12.
The PIOs 34 essentially multiplex the data transmitted between the subscriber line interfaces 36, the command -12~ '7~

line interface 38, the tone generator 40, the tone decoder 60, and the CPU 12.
FIG. 2 shows the details of a subscriber line interface 36 for the subscriber line lOl. The sub-scriber line interfaces for the other subscriber lines102-131 are identical in structure and function. In the preferred embodiment, two subscriber line inter-faces 36 are mounted on a conventional printed circuit card (e.g., BBL part no. PC908).
The eY~isting subscriber extension line 101 actually consists of two lines 42 and 43. A standard optical isolater ring detector 45 (General Electric model no. HllAA1) is connected across lines 42 and 43.
When the ring detector 45 senses a signal on lines 42 and 43 representing a telephone ring, the output line 50 from the ring detector to the PIO 34 goes into a low state. A 2.2 microfarad capacitor 46 is connected in series with an 8.2 K ohm resistor 47 on the input side of the ring detector 45. The capacitor and resistor values are chosen to only permit ring signals on lines 42 and 43 pass to the ring detector 45. A standard ring signal will produce a 90 volt AC signal across lines 42 and 43 for a standard duration of time. The ring detector 45 has an internal optical isolation fea-ture so that its output and the connected circuitry ofthe system 10 will be electrically isolated from the PBX 11. Thus, the telephone paging system 10 is trans-parent to the PBX 11. A conventional voltage source 49 is connected in series with a biasing resistor 48 to provide the voltage for the ring detector 45.
The subscriber line interface card 36 shown in FIG. 2 also includes a relay driver 53 which con-verts a 0-5 volt data signal on the input line 51 to a 0-12 volt signal. One control register 52 provides the signals on lines 51 and 51' for two subscriber line interfaces 36. In the presently preferred embodiment, -13- ~5~7~

two subscriber line interfaces 36 and one control regis~
ter 52 are mounted on one printed circuit card (e.g., BBL model no. PC908). Accordingly, there are a total of 16 control registers 52 for the thirty-one subscriber line interfaces 36 and the one control line interface 38 in the system 10. (The control line interface 38 is on the same card as the first subscriber line interface 36.) The inputs to the control register 52 include the command CLOCK line 68 and the command DATA line 67 which are also connected in parallel from the PIOs 34 to every other control register 52 provided on the sub-scriber line interfaces 36. Each control register 52 has its own command ENABLE line 66 which is connected to the PIOs 34. The CPU 12 clocks command data serially to every control register 52 via the CLOCK and ~ATA
lines. The command data signals include signals which activate a relay driver 53 and signals which do not activate a relay driver. The control register 52 in-ternally stores the activate and non-activate data sig-nals in parallel so that the activate signals corre-spond to the relay driver 53 connected to the subscriber line 101 on which a ring signal has been detected. The CPU 12 sends a command signal on the ENABLE line 66 to the control register 52 which is connected to the sub-scriber line interface 36 which detected a ring signal.
The activate signals are -then sent on line 51 to the relay driver 53, and the non-activate signals are sent to the other relay driver of the subscriber line inter-faces on the same card.
The signal output from the relay driver 53 energizes the relay 54, thereby closing the switch 55.
When the switch 55 is closed, signals from a tone gen-erator 40 can be transmitted to the PBX 11 via the in-put lines 57 and 58, the transformer 56, and the sub-scriber extension lines 42 and 43. The presently -14- ~ Z S~

preferred embodiment uses a conventional relay driver (e.g., the Motorola MC1~13 or the Sprague ULN2002), a conventional relay (model no. AZ7-4D-12DE), and a con-ventional transformer (model no. T1449).
The relay 54 is set to keep the switch 55 in a normally open position. In this state, ring signals on lines 42 and 43 are transmitted to the extension phone which then rings. However, when the ring detector 45 detects a ring signal on lines 42 and 43, the CPU 12 sends a command signal through the PIOs 34 and control register 52, to the relay driver 53 in the manner de-scribed above. The relay 54 closes the switch 55, thereby putting the transformer 56 across the subscriber lines 42 and 43. This command signal on input line 51 is a pulse signal which keeps the switch 55 closed long enough so that the PBX 11 thinks that the extension phone on lines 42 and 43 has been answered. The CPU 12 then sends a second command (or control signal) to the relay driver 53 that "flashes" the relay 54. That is, the relay 54 opens and closes again quickly, which sig-nals the PBX 11 to prepare for a PBX control signal.
Without the telephone paging system 10, a flash may typically be generated by pressing the hook receiver down on a conventional extension phone and quickly re-leasing it.
After the relay 54 has flashed, the tone gen-erator 40, under control of the CPU 12, sends a DTMF
tone signal to the PBX ll which represents a particular PBX command (e.g., to park the call). The tone genera tor 40 includes a standard DTMF encoder (Mostek model no. MK 5087) and a standard tone generator (Signetics model no. NE567) mounted on a printed circuit card found in many conventional paging terminal systems (e.g., BBL Part no. PC9110). The DTMF encoder gener-ates sixteen standard dual-tone, multi-frequency (DTMF) tones which correspond to the keys on a push-button -15- ~5~

telephone keypad. One of these DTMF tones is output by the tone generator 40 in response to a four-bit command signal from the CPU 12. The tone generator is used to generate "beep" tones and a "ring" tones for a caller 5 to hear. The "ring" tones are constantly fed directly from the tone generator 40 to the PBX "music on hold"
port via line 64. Thus, the caller hears "ring" tones whenever his call is parked, even while the system 10 sends paging code signals to the subscriber. The "beep"
10 tones are constantly fed to the control line interface 38. The CPU 12 sends command signals to the control register 52a on the control line interface 38 which selects the "beep" tones via line 59.
FIG. 3 shows the basic components of the con-15 trol line interface 38, which are identical to the com-ponents of a subscriber line interface 36, except that a tone decoder 60 is also bridged across the command line 100. The components of the command line interface 38 which are identical in structure and function to 20 those components comprising the subscriber line inter-face 36 are given the same reference number as the cor-responding component in FIG. 2 plus the suffi~s "a". A
conventional DTMF tone decoder card 60 (e.g. BBL part no. PC908-2), which contains Mitel MT8865 and MT8860 25 chips, is used to sense DTMF tones generated by depress-ing keys on the telephone keypad that represent instruc-tions to the system 10. The first Mitel chip separates the high frequency and low frequency components of the sensed DTMF tone signal. The second chip determines 30 the particular telephone key corresponding -to the sensed tone by determining the particular frequency of the high and low tone components. The digits or symbols (i.e., "~" or "*") representing the decoded instruction signals are stored in an internal buffer of the tone 35 decoder on a first-in-first-out (FIFO) basis. The CPU
12 sends a strobe signal to the tone decoder 60 via the 16~ :a~

PIOs 34 and the input line 62 to place the first digit in the tone decoder buffer on the output line 61 and to position the next digit stored in the buffer. The CPU
12 sends this strobe signal until all the digits stored in the tone decoder buffer have been placed on output line 61. The decoded tone signals put on output line 61 are five bits long. Four bits represent the diyit or symbol corresponding to DTMF tone, and one digit repre-sents whether or not the data is valid. These data bits are sent to the CPU 12 via the PIO 34. The oper-ating program contains the command signals that corre-spond to the instructions represented by the decoded tone signals.
The elements described in FIGS. 1-3 comprise the basic hardware of the presently preferred embodi-ment of the invention. Most of these elements are com-prised of standard off-the-shelf components. Moreover, many of these components can be found on printed cir-cuit cards used in conventional paging terminal sys-tems. For example, one control CTC 30, one SIO 18, andtwo level converts 20, 21 can be found on BBL part no.
PC984; the CPU 12 and the memory 16 can be found on BBL
part no. PC9700; the event CTC 32 can be found on BBL
part no. PC985; and two of the PIOs 18 can be found on BBL part no. PC982.
The CPU 12, which provides the basic control for all components of the system, operates in accord-ance with the software program stored in the EPROM of memory 16. A program listing of the presently preferred software program that is stored in the EPROM is sub-mitted herewith as an appendix. The appended listing is written in Z-80 assembler language. One skilled in the art would be able to readily adapt this program to the hardware previously described to make and use the present invention. Thus, the six sections of the ap-pended program will only be described generally. A

7~

more detailed description of the program can be discerned from the program listing and its comment statements.
The first section is the Supervisor section which initializes the PIOs 34, the event CTC 32, the control CTCs 30 and the SIOs 18. The Supervisor sec-tion also maps a copy of the master data base record from the EPROM into the RAM for storage of temporary data variables.
Since these components can be programmed to operate in several different modes, the Supervision section initializes them in accordance with the Table 1 below. The initialization of the ports of the PI0s 34 will be self-explanatory to one skilled in the art.
The first channel of the event CTC 32 is set up in timer mode to count down to zero. The second channel of the event CTC 32 is set up in counter mode to count the number of times the first channel counts down to zero. The output of the first channel is con-nected to the input of the second channel of the event CTC 32 so that each time the first channel reaches zero it decrements the counter of the second channel. When the counter of the second channel reaches zero, i~
sends an interrupt to the CPU 12 which processes it in the manner described above. The first channel is reset by the CPU 12 whenever the CPU receives an interrupt from the second channel. The first channel then imme-diately begins to count down again.
The two control CTCs 30 each use only one channel on each CTC chip. One control CTC 30 is set up to provide a clock signal to the video terminal SIO 18 everytime the CTC counts down to zero. This clock sig-nal is 16 times the 2400 baud rate required by the video terminal 19. The other CTC is set up to provide a clock signal to the transmitter SIO 18 everytime this CTC counts down to zero. This clock signal is equal to 510 baud rate required by the transmitter 25. Once the -18- ~ ~ ~t~7~

two control CTCs 30 are set up in this manner they will continuously count down to zero and provide the clock pulse to the SIOs 18. These CTCs do not generate any external interrupts to the CPU 12.
The SIO 18 connected to the video terminal 19 is set up to divide the clock signals it receives from the video terminal control CTC by sixteen. This SIO
then outputs 8-bit asynchronous signals to the video terminal l9 at a 2400 baud rate. These signals include a start bit, 7 data bits, a parity bit, and a stop bit.
If the video terminal SIO detects a variation in the stop bit or parity, it sends an interrupt to the CPU 12 indicating there is a data transmission error. The video terminal SIO also sends the CPU 12 interrupts whenever it receives a byte of data input from the video terminal l9. The CPU 12 then reads this data and stores it in the memory 16. The transmitter SIO 18 outputs data to the transmitter 25 at the 510 baud rate input by the transmitter control CTC. The data is out-put as synchronous siynals. The number of bits in eachdata character varies in accordance with the POCSAG
format. Both SIOs 18 send interrupts to the CPU 12 when they output a character, thereby emptying their internal transmitter buffers. In response to this in-terrupt, the CPU 12 sends another byte of data to the empty transmitter buffers. Once the SIOs 18 are initi-alized, they are ready to receive data and operate in the manner described. The SIOs 18 do not respond to transitions on external devices.
The second section controls the detection of riny signals on the subscriber lines 101-131 and the command line lOO, the detection of instruction signals on the command line lOO, the identification of paging code signals distinctively corresponding to the sub-scriber lines on which ring signals have been detected or to instructions detected on the command line and the identification of command signals corresponding to ring signals or instruction signals detected on the command line, and the transmission of identified command sig-nals to the tone generator 40, the tone decoder 60, the subscriber line interfaces 36 and the control interface 38.
The third section controls the output format of the identified paging code signals which are stored in the memory 16 in BCD format. Each paging code sig-nal can be up to 7 digits. This section converts theBCD format paging code into a 4 byte binary pattern in accordance with the POCSAG paging format. POCSAG is a format for processing paging signals which is well known in the pertinent art. All the paging code sig-nals which have been identified are converted to thePOCSAG format in the memory 16 in batch. These POCSAG
format paging code signals are then serially tran-smitted to the SIO 18 connected to the transmitter 25 one byte (8 bits) at a time in the manner described above until all bytes of data in the batch have been sent to the transmitter SIO 18. Prior to sending the first byte, however, a wake-up signal is sent to this SIO 18, which is transmitted to the pagers telling them to listen for their particular POCSAG format paging code signal. The bytes of data sent to the transmitter SIO 18 representing the paging code signals are syn-chronous signals which are frequency shifted in a con-ventional manner.
A fourth section is the Video Terminal Driver section which controls the output of data to SIO 18 connected to the video terminal l9. This section takes a copy of the identified paging code signal, which is in stored in memory 16 in BCD format, and converts it to the ASCII format. The extension number of the sub-scriber line corresponding to this paging code signaland the current value of the real-time clock are also -20~ 7~

identified and converted to ASCII format. These sig-nals are then sent to the video terminal SIO 18 in the manner described above. These signals are then sent from this SIO to the video terminal 19 at 2400 baud.
The fifth section of the software controls the input of the data base record into the memory 16 via the video terminal 19. This section also controls editing of the copy of the master data base record in the RAM via the video terminal 19. This data is input to the memory via the video terminal SIO 18 in the man-ner described above.
The last section of the software defines the layout of the RAM of memory 16 for storing the copy of the data base record which is mapped in from the EPROM
and the data for temporary and program variables.
The telephone paging system 10 embodying the present invention is intended to transmit paging code signals to a remote pager worn by a subscriber. Any type of conventional pager that produces a paging sig-nal in response to a distinctive paging code signal inthe POCSAG format can be used. Each subscriber wears a pager that is responsive only to the paging code signal distinctively corresponding to his assigned extension line. The pager may output any type of well known pag-ing signals in response to the paging code signal.
Having described the various elements thatcomprise the telephone paging system of the presently preferred embodiment of the invention, its operation will now be described. As a preliminary step, the ex-tension phone number, pager code identification number,initial status, and physical extension line number for each subscriber are programmed into the EPROM. When the system is activated, the data base record stored in the EPROM is mapped into the RAM, and the RAM is set up for the storage of temporary and program variables.
The CPU 12 then initializes the SIOs 18, the control CTCs 30, the event CTC 32, and the PIOs 34 in the man-ner described above.
The paging operation of the preferred embodi-ment is initiated in response to the first ring signal detected on a selected subscriber line 101-131. When the PBX 11 sends a ring signal to a subscriber's exten-sion phone, (e.g., subscriber line 101), the ring de-tector 45 will force output line 50 into a low state.
The CPU 12 will cooperate with the event CTC 32 to de-termine if output line 50 remains in the low state long enough to correspond to a ring signal on the subscriber extension line lOl. If so, the CPU 12 sends an enable signal to the control register 52, thereby putting a command signal on input line 51. The command signal is amplified by the relay driver 53 to energize the relay 54 which closes the switch 55. The transformer 56 is then bridged across lines 42 and 43 of the subscriber line 101.
The switch 55 is closed for an amount time that indicates to the PBX ll that the phone on sub-scriber line 101 has been answered. The PBX 11 will then stop producing ring signals on subscriber line 100. Nevertheless, the caller still hears ring signals that the tone generator 40 sends to the music on hold port of the PBX ll via line 64 while his call is parked.
The CPU 12 then sends a second command signal to input line 51 via the PIOs 34 and the control regis-ter 52, which causes the relay 54 to flash the switch 55. This flash signals the PBX 11 to prepare to re-ceive a PBX command signal. The CPU 12 then signals the tone generator 40 to send a DTMF signal to lines 42 and 43 of the subscriber line 101 via input lines 57 and 58 and transformer 56, which will command the PBX
11 to park the call on subscriber line 101.
Next the CPU 12 sends a command signal the relay driver 53 via the PIOs 34 and the control register 22- ~ 2 S ~

52, that de-energizes the relay 54, thereby opening the switch 55. The system 10 is then disconnected (or re-leased) from the subscriber line 101. The PBX 11 in-terprets the open switch 55 to mean that the subscriber on extension line 101 has hung up his phone.
~ hile the P~X 11 holds the call on park, the CPU 12 searches the memory 16 to identify the pager identification number (paging code signal) correspond-ing to the physical subscriber extension line 101 on which the ring signal was sensed. The CPU, under con-trol of the output format section of the software, sends a key-up signal to the transmitter 25 via the SIOs 18 and connector pin 78 of the transmitter level converter 24. Dummy data is then sent to the transm-itter 25 via connector pin 79 for about 1 second while the transmitter warms up. After this is completed, a wake-up signal is sent to the transmitter 25 via con-nector pin 79 to alert all pagers to prepare for a pag-ing code signal. The CPU 12 then converts the iden-tified paging code signal to the POCSAG format, con-verts a copy of the identified paging code signal, the corresponding subscriber line and the current real-time clock value to the ASCII format, and sends them to the SIOs 18. The SIOs 18 will serially transmit the POCSAG-format paging code signal to the transmitter 25 via connector pin 79 and the ASCII-format signals to video terminal 19 in batch in accordance with their respective baud rates as controlled by the control CTCs 30. The transmitter level converter 24 will translate the voltage level of paging code data signals input at pin 79 to a level compatible with the transmi-tter 25.
After -the last byte of the POCSAG-format paging code signal has been transmitted to the SIOs 18, the CPU 12 sends more dummy data bytes to the transmitter 25 via the SIOs 18 to assure that all bytes of the paging code -23~

signal were transmitted. The key-up signal is then terminated and the paglng process can begin anew.
The transmitter 25 transmits the paging code signal via the antenna 26 to all pagers within the range of the transmitter 25 and antenna 26. The pager worn by a subscriber which is responsive to the particular POCSAG format paging code signal transmitted will pro-duce a paging signal. The subscriber will then know that someone has directed a call to his extension line and that the call is parked. The subscriber can re-trieve the parked call from any other extension phone on the PBX ll by entering -the appropriate PB~ command via the telephone keypad.
A subscriber may enable or disable his pager via the command line 100 by entering the appropriate instructions via any extension telephone keypad. The subscriber first dials the extension telephone number corresponding to the command line 100. The ring de-tector 45a responds by putting line 50a in a low state for a period of time corresponding to a ring signal.
The CPU 12 then sends a command signal to the relay driver 53a via the control register 52a and PIOs 34.
The relay 54a closes the switch 55a and keeps it closed until the caller hangs up on the phone. In the mean-time, the CPU 12 sends a command signal to the tonegenerator 40 to send a DTMF tone corresponding to a "beep" to lines 57a and 58a of the control line inter-face 38. This "beep" is routed to the subscriber by the PBX 11 by connecting the caller's extension to the command line 100. Upon hearing the "beep", the sub-scriber-caller enters his own extension phone number from the telephone keypad, which represents a first instruction signal. The tone decoder 60 decodes the DTMF tones that represent the digits of the phone num-ber entered. The CPU 12 strobes the port of the tonedecoder 60 with a strobe signal until it receives the -2~- ~5'~7~

data representing all digits on the data bus 61. The CPU 12 then sends another command signal to the tone generator 40 to produce two "beep" signals. Upon hear-ing the two "beep" signals, the subscriber depresses either the "~" or a "#" telephone key, which are enable or disable instruction signals, respectively. The tone decoder 60 decodes the DTMF tones that represent these two keys, and the CPU 12 sends a strobe signal over line 62 to put this data on line 61. The CPU 12 then searches the memory 16 to identify the subscriber cor-responding to the extension number entered and updates the operating status of his paging code signal accord-ing to the second instruction signal entered. The up-dated status is stored in the ~AM of memory 16.
The CPU ].2 next sends the first command sig-nal to the tone generator 40 to produce the "beep" tone signal again. Upon hearing this signal, the subscriber-caller may enable or disable the paging code signal of another subscriber by following the procedure just de-scribed. If, however, he pauses too long before enter-ing the next instruction signal, the CPU 12 will com-mand the tone generator 40 to produce an alternating "beep-beep" signal, thereby indicating the completion of this function. The subscriber-caller then must dial the command line 100 again to enable or disable another subscriber.
When this enable/disable function is avail-able, the telephone paging system described above oper-ates slightly differently. After a ring signal is de-tected on a subscriber line, the CPU 12 first identi-fies the status of that subscriber line before it seizes the subscriber line to answer the call. If the line is enabled, the telephone paging system proceeds to park the call and transmit a paging code signal to the sub-scriber in the manner described above. If the pagingcode signal for that subscriber line is disabled, -25- ~S~7~

however, the system never closes the relay 54. Thus, the phone is allowed to ring and no paging code signal is transmitted.
A subscriber can also directly page another subscriber via the cornmand line 100. The subscriber-caller first dials the extension phone number corre-sponding to the command line 100 from any phone con-nected to the PBX 11. The CPU 12 answers the line and sends the first "beep" tone in the same manner just described for the enable/disable function. Upon hear-ing the "beep", the subscriber-caller enters from his telephone keypad the extension phone number of the sub-scriber he wishes to page (the "subscriber-pagee"), which represents a first instruction signal. The tone decoder 60 decodes the DTMF tones representing the digits of the number entered, and the CPU 12 sends a strobe signal to put this data of line 61. The CPU 12 then sends the second command signal to the tone gen-erator 40 to produce two "beep" tones. Upon hearing the two "beeps", the subscriber-caller enters from his key-pad the numbers 1, 2, 3 or 4, which represent four dis-tinctive POCSAG paging tone patterns. This instruction signal is decoded by the tone decoder 60 and sent to the CPU 12 over line 61. The CPU 12 then searches the memory 16 to identify the subscriber-pagee corresponding to the extension phone number entered. The CPU 12 also identifies one of four POCSAG paging patterns corre-sponding to the second instruction entered. The CPU 12 converts the identified paging code signal into the POCSAG paging format that includes the paging format specified. This paging code signal is sent to the trans-mitter 25 via the SIOs 18 in the manner described above.
The CPU 12 then sends a third cornmand signal to the tone generator 40 to produce the alternating "beep"-"beep!' tone for the subscriber-caller to hear, which -26- l~S~

represents that the operation has been completed. The subscriber-caller then hangs up his phone.
A subscriber may also test his pager by directly paging himself in accordance with the procedure de-scribed above. Upon hearing the first beep tone, thesubscriber would enter his own extension telephone num-ber. The system 10 would then send a paging code sig-nal that would activate the subscriber's own pager.
FIGURE 4 shows the subscriber interface card 36a which may be used in another embodiment of the in-vention. This type of subscriber interface card would be connected to a subscriber extension line lOlb on a PBX 11 that has a direct-call-pickup function. This allows a subscriber to pick up a call on an extension line from any other extension line. A PBX with this directed call pick-up function can also forward a call to another extension line after a predetermined number of rings when requested by a subscriber. These func-tions are executed by the PBX 11 independent of the telephone paging system 10.
The modified subscriber interface card 36a, as shown in Fig~ 4, includes a ring detector 45b con-nected across lines 42b and 43b of the subscriber ex-tension telephone line lOlb. A capacitor 46b and resis-tor 47b are connected in series to one of the inputports of the ring detector 45b. The ring detector 45b is optically isolated from the PBX ll and powered by a voltage source 49a and biasing resistor 48b. These components cooperate to detect a ring signal on sub~
scriber line lOlb, and in response thereto place output line 50b in a low state in the same manner described above for the corresponding components in Fig. 2. The CPU 12 cooperates with the other components shown in Fig. 1 in the same way described above to transmit a paging code signal distinctly corresponding to the sub-scriber assigned to extension line lOlb.

An important advantage of the subscriber line interface 36 or 36a is that it does not require a relay driver, relay, switch, transformer, control register, or equivalents thereof, to answer the call and then put it on park. In this embodiment, the subscriber line interface 36a and the other components of the telephone paging system lO shown in Fig. l cooperate to transmit a paging code signal upon detection of the first ring signal on the subscriber line lOlb while only monitor-ing ring signals on the subscriber line lOlb. Thus,the phone on the subscriber line lOlb continues to ring while the telephone paging system transmits a paging code signal corresponding to subscriber line lO1. This also allows the PBX functions to operate concurrently with the system 10 (for example, transferring the call to another extension line after a predetermined number of ring signals, if requested by the user).
As shown in FIGURE 1, the presently preferred embodiment of the invention does not select all the available extension lines 132-200 for connection to the telephone paging system 10. Another embodiment of the present invention is shown in Fig. 5 which allows the additional subscriber extension phone lines to be in-terfaced to the telephone paging system 10 via the re-mote line interface units 70, 71, 72. In this embodi-ment the dedicated control line lO0 and the subscriber extension lines 101-131 are connected to the PBX 11 and the components of the telephone paging system 10 as explained above in connection with Figs. 1-3.
The remote line interface card 70 would be connected across one of the extension lines 132-200.
The remote line interface card 70 could be configured much like FIGS. l and 2 or 4, except that only one SI0 chip 18 and one con-trol CTC chip 30 would be required.
The remote line interface card would detect ring sig-nals on the selected remote extension line and send ~27--28- ~5~79 signals down the serial data lines 74, 75, 76 to the telephone paging system 10. The signal transmitted down the serial data line would represent that the par-ticular remote extension line (e.g. 132) was ringing.
Since this data is being transmitted serially, the be-ginning and end of this data would have to be marked.
Only two SIO ports would be necessary: one to receive input from the remote line interface unit above and one to output the data to the remote line interface unit or the telephone paging system 10 below. The oscillator used on the remote line interface unit would not have to be as stable as the oscillator 14. The data base record stored in the memory in the telephone paging system 10 would also contain coded signals correspond-ing to the extension telephone number, pager identifi-cation number, status, and physical extension line num-ber of each remote line connected to the system 10.
Using the remote line interface units 70, 71, 72, additional subscribers can be added to the tele-phone paging system 10 at minimal expense. The remoteunits will monitor each subscriber phone line and sig-nal any "ringing" lines back to the systern unit 10.
The system 10 reads the digital information arriving from the serial cornmunication line 76 and decodes the information to determine which remote phone line was ringing. The telephone paging system 10 could then proceed to page the subscriber to the remote line in the same manner described above for one of the sub-scribers line interfaces 36.
The preferred embodiment described above is a telephone paging system interfaced to a conventional telephone line branching system which has the capabil-ity of parking a call and conventional pagers that are responsive to POCSAG format paging code signals. How-ever, it should be apparent that the present invention can be interfaced with other types of telephone line -29 ~ ~ S~

branching means or pagers. For example, the present invention could be adapted for use with a PBX that has voice synthesized announcements that could be played to the caller to indicate that the subscriber called is being paged. The present invention could also be used with a higher powered transmitter that would extend the range of the transmitted paging code signals from build-ing wide to city-wide. At this point, a "meet-me" func-tion in the PBX could be used by the subscriber receiv-ing the call to accept the call at any phone in thecity.
Other embodiments of the present invention should be also apparent to those skilled in the art from the foregoing description. For example, multiple transmitters 25 could be implemented in the system 10 so that more than one subscriber can be paged simulta-neously. Also, a paging system other than POCSAG could be used. The system could also be modified to re~uire the detection of more than one ring signal on a sub-scriber's extension line before transmitting a pagingcode signal. A PBX-type branching means may also be developed that identifies the intended subscriber line of an incoming call and then transmits a paging code signal in accordance with the present invention without putting a signal on the intended subscriber line.
Of course, it should be understood that vari-ous other changes and modifications to the preferred embodiment described above will be apparent to those skilled in the art. It is intended that the foregoing description be regarded as illustrative rather than limiting and that it be understood that it is the fol-lowing claims, including all equivalents, which are intended to define the scope of the invention.

_30_ ~54~7~

TABLE 1.
The seven PIOs 34 are initialized as follows:
(Note: A11 pin names are in accordance with standard Zilog Nomenclature and all unused PIO pins are not listed.) PIO # PIN NAME DESCRIPTION
1 A7 Output - Command Data 68 to all subscriber interfaces 36 and the control interface ARDY Output - Command Clock 67 to all subscriber interfaces 36 and the control interface 38.
BO Output - Command Enable to control interface 38 and subscriber interface #l Bl Output - Command Enable to Subscriber Interface 2 and 3 B2 Output - Command Enable to Subscriber Interface 4 and 5 B3 Output - Command Enable to Subscriber Interface 6 and 7 B4 Output - Command Enable to Subscriber Interface 8 and 9 B5 Output - Command Enable to Subscriber Interface 10 and 11 B6 Output - Command Enable to Subscriber Interface 12 and 13 B7 Output - Command Enable to Subscriber Interface 14 and 15 2 A0 Input - Control Interface Ring Detector 45a Al Input - Subscriber Interface ~1 Ring Detector A2 Input - Subscriber Interface ~2 Ring Detector A3 Input - Subscriber Interface #3 Ring Detector A4 Input - Subscriber Interface #4 Ring Detector PIO # PIN NAME DESCRIPTION
A5Input - Subscriber Interface #5 Ring Detector A6Input - Subscriber Interface #6 Ring Detector A7Input - Subscriber Interface #7 Ring Detector B0Input Subscriber Interface #8 Ring Detector B1Input - Subscriber Interface #9 Ring Detector B2Input - Subscriber Interface #10 Ring Detector B3Input - Subscriber Interface #11 Ring Detector B4Input - Subscriber Interface #12 Ring Detector B5Input - Subscriber Interface #13 Ring Detector B6Input - Subscriber Interface #14 Ring Detector B7Input - Subscriber Interface ~15 Ring Detector

3 B0Output - Command Enable to Sub-scriber 16 and 17 B1Output - Command Enable to Sub-scriber 18 and 19 B2Output - Command Enable to Sub-scriber 20 and 21 B3Output - Command Enable to Sub-scriber 22 and 23 B4Output - Command Enable to Sub-scriber 24 and 25 B5Output - Command Enable to Sub-scriber 26 and 27 B6Output - Command Enable to Sub-scriber 28 and 29 B7Output - Command Enable to Sub-scriber 30 and 31

4 A0Input - Subscriber Interface #16 Ring Detector A1Input - Subscriber Interface #17 Ring Detector A2Input - Subscriber Interface #18 Ring Detector A3Input - Subscriber Interface #19 Ring Detector A4Input - Subscriber Interface #20 Ring Detector A5Input - Subscriber Interface #21 Ring Detector 7~

PIO # PIN NAME DESCRIPTION
A6 Input - Subscriber Interface #22 Ring Detector A7 Input - Subscriber Interface #23 Ring Detector B0 Input - Subscriber Interface #24 Ring Detector Bl Input - Subscriber Interface #25 Ring Detector B2 Input - Subscriber Interface #26 Ring Detector B3 Input - Subscriber Interface #27 Ring Detector B4 Input - Subscriber Interface #28 Ring Detector B5 Input - Subscriber Interface #29 Ring Detector B6 Input - Subscriber Interface #30 Ring Detector B7 Input - Subscriber Interface #31 Ring Detector Al Output - Tone Generator 40 Data Bit 0 A2 Output Tone Generator 40 Data Bit 1 A3 Output - Tone Generator 40 Data Bit 2 A4 Output - Tone Generator 40 Data Bit 3 A5 Output - Tone Generator 40 Enable 6 A0 Output - DTMF Tone Decoder 60 Strobe 7 A0 Input - DTMF Tone Decoder 60 Data Bit 0 Al Input - DTMF Tone Decoder 60 Data Bit l A2 Input - DTMF Tone Decoder 60 Data Bit 2 A3 Input - DTMF Tone Decoder 60 Data Bit 3 A4 Input - DTMF Tone Decoder 60 Data Bit 4 The event CTC 32 is intitialized as follows:
Channel #1: A. Interrupts Disabled B. Timer Mode C. Prescaler = 256 D. Automatic trigger when time constant is loaded E. Time Constant for 10 millisecond events Channel #2 A. Interrupts Enabled B. Counter Mode C. Prescaler = 16 D. Vectored Interrupts _33_ ~2S~97~

The control CTCs 30 are intitialized as follows:
CONTROL CTC #l (to video terminal SIO 18~:
Counter~Timer #1: A. Interrupts Disabled B. Counter Mode C. Prescaler = 16 D. Time Constant for 2400 baud output to SIO 18 CONTROL CTC #2 (to transmitter SIO 34):
Counter/Timer #1: A. Interrupts Disabled B. Counter Mode C. Prescaler = 16 D. Time Constant for 510 baud output to SIO 18 The SIOs 18 are initialized as follows:
SIO #l (video terminal): A. X 16 Clock input B. Even parity C. l Stop Bit D. Asynchronous Communications E. 7 bits per character F. Interrupt on all received and transmitted characters G. Disable external interrupts SIO #2 (to transmitter): A. X l Clock input B. No parity C. No stop bit D. Synchronous communications E. Number of bits per character varies during operation F. Interrupt on all transmitted characters G. Disable external interrupts

Claims (41)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. In a telephone system including branching means for switching signals on an incoming telephone line between a plurality of extension telephone lines and a plurality of means for receiving paging code sig-nals, each receiving means being responsive to a par-ticular paging code signal, the improvement comprising:
means for selecting a plurality of extension telephone lines;
means for detecting signals directed to se-lected extension lines representing a call;
means for storing a plurality of signals represent-ing different paging codes, wherein each paging code signal distinctively corresponds to one of the selected extension lines and a receiving means;
means for identifying the paging code signal corresponding to the selected extension line for which the detecting means detected a call signal; and means for transmitting the identified paging code signal to a plurality of the receiving means.

2. The invention of Claim 1 wherein the branch-ing means includes means for transferring a call from one extension line to a different predetermined exten-sion line after a predetermined number of ring signals.

3. The invention of Claim 1 wherein the branch-ing means includes means for allowing an extension line to access another extension line.

4. In a telephone system including branching means for switching signals on an incoming telephone line between a plurality of extension telephone lines and for holding a call on an extension line and a plural-ity of means for receiving paging code signals, each receiving means being responsive to a particular paging code signal, the improvement comprising:
means for selecting a plurality of extension lines;
a detection means connected to each selected extension line for sensing signals representing tele-phone rings;
means for storing a plurality of signals rep-resenting different paging codes, wherein each paging code signal distinctively corresponds to one of the selected extension lines and a receiving means;
control means for sending control signals to the branching means to hold a call on an extension line when the detection means senses a predetermined number of ring signals on the extension line;
means for identifying the paging code signal corresponding to the selected extension line on which the detection means has sensed a predetermined number of ring signals; and means for transmitting the identified paging signal to a plurality of the receiving means.

5. The invention of Claim 4 wherein the detec-tion means is optically isolated from the branching means.

6. The invention of Claim 4 wherein the control means includes relay means for sending a first control signal to the branching means, when the detection means senses a predetermined number of ring signals on the extension line, to prepare the branching means to re-ceive a second control signal.

7. The invention of Claim 6 wherein the control means further includes a tone generator means for send-ing a second control signal to the branching means to place the call on hold.

8. The invention of Claim 4 wherein the branch-ing means includes means for allowing an extension line to access another extension line.

9. In a telephone system including branching means for switching signals on an incoming telephone line between a plurality of extension telephone lines and a plurality of means for producing paging signals in response to paging code signals, wherein each pro-ducing means is responsive to a particular paging code signal, the improvement comprising:
means for selecting a plurality of extension lines for subscribers and one extension line for com-mand signals;
a separate ring detection means connected to each subscriber line and to the command line for sens-ing signals representing telephone rings;
a code detection means connected to the com-mand line to sense signals representing instructions;
means for storing a plurality of signals rep-resenting different paging codes and commands, wherein each paging code signal distinctively corresponds to one of the subscriber lines or an instruction signal and each command signal corresponds to a ring signal on the command line or an instruction signal;
means for identifying the paging code signal corresponding to the subscriber line on which the ring detection means has sensed a predetermined number of ring signals or to an instruction signal, and for iden-tifying the command signal corresponding to a ring sig-nal, when the ring detection means has detected a pre-determined number of ring signals on the command line, or an instruction signal sensed by the code detection means;
control means for sending identified command signals to the branching means; and means for transmitting the identified paging signals to a plurality of the producing means.

10. The invention of Claim 9 wherein the identi-fication means identifies a first command signal when the ring detection means senses a predetermined number of ring signals on the command line.

11. The invention of Claim 10 wherein the identi-fication means identifies a second command signal when the code detection means senses a first instruction signal.

12. The invention of Claim 11 further comprising means cooperating with the identifying means for en-abling a paging code signal when the code detection means senses a second instruction signal on the command line.

13. The invention of Claim 11 further comprising means cooperating with the identifying means for dis-abling a paging code signal when the code detection means senses a second instruction signal on the command line.

14. The invention of Claim 11 wherein the identi-fying means identifies a first paging code signal cor-responding to a first instruction signal sensed by the code detection means and a second paging code signal corresponding to a second instruction signal sensed by the code detection means.

15. The invention of Claim 10 wherein the identi-fying means identifies a paging code signal correspond-ing to the first instruction signal sensed by the code detection means.

16. A telephone paging method comprising:
selecting a plurality of extension telephone lines on a branching means for switching signals on an incoming telephone line between a plurality of exten-sion lines;
detecting signals representing rings on the selected extension lines;
parking a call on the branching means when a ring signal is detected on an extension line;
storing a plurality of signals representing different paging codes, wherein each paging code signal distinctively corresponds to a selected extension line;
identifying the paging code signal correspond-ing to the selected extension line on which a predeter-mined number of ring signals has been detected; and transmitting the identified paging code sig-nal to a plurality of means for producing paging sig-nals in response to different paging code signals.

17. A telephone paging method comprising:
selecting a plurality of extension telephone lines on a branching means for switching signals on an incoming telephone line between a plurality of exten-sion lines;
detecting signals representing calls to the selected extension lines;
storing a plurality of signals representing different paging codes, wherein each paging code signal distinctively corresponds to a selected extension line;

identifying the paging code signal correspond-ing to the selected extension line for which a call signal has been detected; and transmitting the identified paging code sig-nal to a plurality of means for producing paging sig-nals in response to different paging code signals.

18. A telephone paging method comprising:
selecting a plurality of telephone extension lines for subscribers on a branching means for switch-ing signals on an incoming telephone line between a plurality of extension lines;
selecting an extension line on the branching means for command signals;
detecting signals representing rings on the subscriber extension lines and the command extension line;
detecting signals representing instructions on the command line;
storing a plurality of signals representing different paging codes and commands, wherein each paging code signal corresponds to a predetermined selected subscri-ber extension line or instruction signal and each command signal corresponds to a ring signal on the command ex-tension line or predetermined instruction signal;
identifying the stored command signal corre-sponding to a ring signal when a predetermined number of ring signals has been detected on the command exten-sion line or an instruction signal which has been de-tected;
identifying the stored paging code signal corresponding to the subscriber extension line upon which a predetermined number of ring signals has been detected or an instruction signal which has been detect-ed;

sending identified command signals to the branching means; and transmitting the identified paging code sig-nals to a plurality of means for producing paging sig-nals in response to different paging code signals.

19. The invention of Claim 18 wherein the sending an identified command signal step includes sending a first command signal to the branching means in response to detecting a predetermined number of ring signals on the command extension line.

20. The invention of Claim 19 wherein the sending an identified command signal step further includes send-ing a second command signal to the branching means in response to detecting a first instruction signal on the command extension line.

21. The invention of Claim 20 further comprising enabling a paging code signal in response to detecting a second instruction signal on the command extension line.

22. The invention of Claim 20 further comprising disabling a paging code signal in response to detecting a second instruction signal on the command extension line.

23. The invention of Claim 19 wherein the identi-fying a stored paging code signal step includes identi-fying a paging code signal in response to detecting a first instruction signal on the command line.

24. The invention of Claim 20 wherein the identi-fying a stored paging code signal step includes identi-fying a first paging code signal in response to detect-ing a first instruction signal on the command extension line and a second paging code signal in response to detecting a second instruction signal on the command line.

25. A telephone paging system comprising:
means for detecting telephone call signals switched from one telephone line to one or more telephone lines; and means for selecting and transmitting a stored paging code signal that distinctively corresponds to the telephone line for which a call signal has been detected, each stored paging code signal being operative to activate one of a plurality of remote paging devices.

26. A telephone paging system comprising:
means for detecting a telephone call directed to one or more telephone lines;
means for transmitting a paging code signal that distinctively corresponds to the telephone line for which a telephone call has been detected, the paging code signal being operative to activate a remote paging device; and means for allowing the detected telephone call to be received at a telephone line other than the one upon which the telephone call has been detected.

27. A telephone paging system comprising:
means for detecting a telephone call directed to one or more telephone lines;
means for transmitting a paging code signal that distinctively corresponds to the telephone line for which a telephone call has been detected, the paging code signal being operative to activate a remote paging device;
means for automatically sustaining a telephone call while the transmitting means transmits the paging code signal;
and means for allowing a sustained telephone call to be accessed from a telephone line other than the one for which the telephone call was detected.

28. The invention of claim 27 further including means for enabling or disabling the transmitting means with respect to a particular telephone line.

29. The invention of claim 28 wherein the enabling or disabling means is controlled through a telephone line.

30. The invention of claim 27 further including means for selecting and initiating transmission of a particular paging code signal to a remote paging unit, from one telephone line via another telephone line.

31. A telephone paging system comprising:
means for detecting telephone call signals directed to one or more telephone lines;
means for transmitting a paging code signal that distinctively corresponds to the telephone line for which telephone call signals have been detected, the paging code signal being operative to activate a remote paging device;
means for automatically holding telephone call signals while the transmitting means transmits a paging code signal; and means for allowing held telephone call signals to be accessed from a telephone line other than the one for which the telephone call signals have been detected.

32. The invention of claim 31 further including means for enabling or disabling the transmitting means with respect to a particular telephone line.

33. The invention of claim 32 wherein the enabling or disabling means is controlled through a telephone line.

34. The invention of claim 31 further including means for selecting and initiating the transmission of a particular paging code signal to a remote paging unit, from one telephone line via another telephone line.

35. The invention of claim 31 further comprising means for directing telephone call signals to one or more telephone lines.

36. A telephone paging system comprising:
means for detecting telephone call signals directed to one or more telephone lines;
means for transmitting a paging code signal that distinctively corresponds to the telephone line for which telephone call signals have been detected, the paging code signal being operative to activate a remote paging device;
means for automatically continuing telephone call signals while the transmitting means transmits a paging code signal; and means for allowing continued telephone call signals to be accessed from a telephone line other than the one for which the telephone call signals have been detected.

37. The invention of claim 36 further including means for enabling or disabling the transmitting means with respect to a particular telephone line.

38. The invention of claim 37 wherein the enabling or disabling means is controlled through a telephone line.

39. The invention of claim 36 further including means for selecting and initiating the transmission of a particular paging code signal to a remote paging unit, from one telephone line via another telephone line.

40. The invention of claim 36 further comprising means for directing telephone call signals to one or more telephone lines.

41. A telephone paging system comprising:
means for detecting telephone call signals on a telephone line;
means for detecting instruction signals on the telephone line;
means for sending command signals over the telephone line when a predetermined number of call signals or instruction signals have been detected on the telephone line; and means for selecting and sending a particular paging code signal to a remote paging unit via the telephone line in response to a predetermined instruction signal sent from another telephone line.