CA1197559A - Frequency modulation transmitter circuit arrangements for voice or data - Google Patents
Frequency modulation transmitter circuit arrangements for voice or dataInfo
- Publication number
- CA1197559A CA1197559A CA000400469A CA400469A CA1197559A CA 1197559 A CA1197559 A CA 1197559A CA 000400469 A CA000400469 A CA 000400469A CA 400469 A CA400469 A CA 400469A CA 1197559 A CA1197559 A CA 1197559A
- Authority
- CA
- Canada
- Prior art keywords
- data
- signal
- circuit
- voice
- responsive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
- H03J9/00—Remote-control of tuned circuits; Combined remote-control of tuning and other functions, e.g. brightness, amplification
- H03J9/06—Remote-control of tuned circuits; Combined remote-control of tuning and other functions, e.g. brightness, amplification using electromagnetic waves other than radio waves, e.g. light
-
- 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
- H04M11/066—Telephone sets adapted for data transmision
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
- H04M11/08—Telephonic communication systems specially adapted for combination with other electrical systems specially adapted for optional reception of entertainment or informative matter
- H04M11/085—Telephonic communication systems specially adapted for combination with other electrical systems specially adapted for optional reception of entertainment or informative matter using a television receiver, e.g. viewdata system
Abstract
ABSTRACT
FREQUENCY MODULATION TRANSMITTER CIRCUIT ARRANGEMENTS
FOR VOICE OR DATA
A portable frequency modulation transmitter (1) for voice or data is disclosed for operation at infrared frequencies. The transmitter comprises keyboard (200) or microphone (402) input capability and dual modes of use.
In the data mode, carrier is generated when the keyboard is operated and is not generated when the keyboard is idle in order to conserve power. In the voice mode, either voice or data may be transmitted, data having priority over voice. A series connection of two variable modulus counters (302,303) and other counters (304,305,306) provide a frequency shift keyed data signal, marker data signal, marker data frames between data frames, parity insertion and other features. In the event that the local battery power level falls below a particular level, a particular word is inserted in the applied binary data input.
FREQUENCY MODULATION TRANSMITTER CIRCUIT ARRANGEMENTS
FOR VOICE OR DATA
A portable frequency modulation transmitter (1) for voice or data is disclosed for operation at infrared frequencies. The transmitter comprises keyboard (200) or microphone (402) input capability and dual modes of use.
In the data mode, carrier is generated when the keyboard is operated and is not generated when the keyboard is idle in order to conserve power. In the voice mode, either voice or data may be transmitted, data having priority over voice. A series connection of two variable modulus counters (302,303) and other counters (304,305,306) provide a frequency shift keyed data signal, marker data signal, marker data frames between data frames, parity insertion and other features. In the event that the local battery power level falls below a particular level, a particular word is inserted in the applied binary data input.
Description
(G. I.ese 3-11) FREQUF,NCY MODULATION Tr~ANSMITTER CI~CUIT ARR~NGEMENTS
FOR VOICE OR DATA
This invention relates -to ~requency modulation -transmitter circuit arrangements -For voice or data.
Cordless telephone s-ta-tion systems employing infrared transmission are known comprising a portable cordless transmitter with remote microphone and supervisory signalling capabili-ties. One such -transmitter is described in Anglikowski e-t al.~ U.S,Paten-t No, 4,221,932. The supervisory signalling is achieved by shifting the carrier ireqwency of the transmitted signal ~or indicating a low battery condi-tion and transmi.tter turno~'~'. There is no keyboard da-ta :lnput capability.
Al-ternatively, portable cordless transmitters are known for -transmi-tting keyboard en-tered data signals for controlling a ca-thode ray tube -television terminal. ~`or example, Richter et al., U.S.Patent No. 4, 091,272, discloses an infrared remote con-trolled command system for operating a -television receiver, heys of a keyboard are provided for selecting the television channel ox for controlling the volume level.
With the onse-t of viewda-ta services wherein a combination -telephone and television terminal may be prov.ided to telephone subscribers, it is believed desirable ~hat both voice and data be enterable ~rom the remote portable transmitter. The user O-e the transmitter would not have to be located in close proximity to -the viewdata terminal and would be able to remotely control its television and telephone functions.
In accordance wi-th the present invent~on the above stated problems and related problems of the prior art are alleviated by providing a circuit arrangement for use in a fre~uellcy modulatiorl tran~mitter ~or transmitting a firs-t, (voice~ signal and a second (data~
signal, the circuit arrangement comprising a data modulator and contro~ circuit for generating a modlllated 38 data ~ignal and a control signal indicating the presence 7~
o~ data, a signal mutlng switctl, responsive to -the control signal of the data modulator and control cireui-t, ~or mu-ting the first signal, and a gain swi-tch, responsive to the control signal o~ the da-ta moctulator and control circui-t, :eor at-tenua-ting the level o~ the modulated data signal. In a pre~erred embodimen-t o~
-the inven-tion the circui-t arrangement as a~oresaid wil:L
~orm part o~ a ~requency modulated -transmitter, advantageously o~ portable ~orm.
The transmitter comprises remote keyboard and mierophone capability and dual modes of use. In -the da-ta mode o~ use, earrier ~reqllency is only generated when the keyboard characters are depressed in order to conserve battery power. In the voice mode o:~ use, either voice or data may be transmi-tted, the data preemp-ting the voice.
~arrier ~requency is continuously generated in this mode.
A carrier eontrol circuit responsive to the selection o~
voiee or data mode provides -this carrier control ~ea-ture.
In the voiee mode of use, a data eontrol signal indieative o~ the presence o~ data is provided. The data eontrol signal eontrols the operation o~ a mierophone muting switeh and a frequency shi~t key gain switeh. I~
da-ta is present, the microphone is muted and, as a result, the data preempts the voice signal.
Spaee is another primary consideration in the design o~ a small portable transmitter. Aeeordingly, the transmitter eomprises a minimum number o~ eomponents provlding a maximum number o~ features. The primary eornponents o~ the present transmltter ~or providing a modulated data signal are two variable modulus eounters.
Tha ~irst eounter divides a eloek ~requeney either by one or another partieular modulus, its inp~-t being a binary bit da-ta ~tream. The seeoncl variable modulus eounter, responsive to the bina:ry bit stream divides the output o~
the ~irst eounter by the ~ame moduli oppositely. In this manner, an output signal is provicled at the input bit stream rate. This bit rate output, then, may be used to 38 provide a number o~ ~eatures a~ter passa~e-through a number s~
of particularizecl coun-ters.
Fo:r example, a data bit counter counts -the genera-ted data bits. In combination with a data selector circui-t ~or providing the binary data stream to the J~
counters, the data can be separated in-to words of a particular length. Another par-ti.cularized counter, a marker/data counter, inhibits the flow of data for the insertion of marker data before each data word. A frame counter provides information to an on~off control circuit for sending a particular number of frames of information to the receiver indicatiny that the transmitter has just been turned on or off.
Brief Deserip*ion of the Drawings FIG. 1 is a sehematie drawiny and pietorial representation of a viewdata serviees terminal eomprising the present frequeney modulation transmitter for voiee or data;
FIGS. 2, 3, and 4 are sehematie drawings and general bloek diagrams of one embodiment of the present frequeney modulation transmitter for voiee or data;
FIG. 5 is a key figure, demonstrating the relationships among FIGS. 2, 3, and 4;
FIG. 6 is a graphieal representation of one ~0 serial transmission ~eheme whieh may be employed in the present invention;
FIGS. 7, 8 and 9 are timing diagrams, illustrating thé operation of FIGS. 2, 3, and 4 and portraying waveforms at various points in the transmitter circuit over a duration of 21 time periods; and FIG. 10 is a key figure, demonstxating the relationships among FIGS. 7, 8, and 9.
Detailed Deseription Referring more partieularly to FIG. 1, there is shown a sehematie drawing and pietorial represen-tation of a terminal for providing viewdata services eomprising a transmitter 1 in aceordance with the present invention.
The transmitter 1 is portable and adapted to be hand-held.
It eomprises an on/off slide switeh 310, a mierophone ~02 and a keyboard 200. The transmitter also comprises integrated injeetion :Logic and infrared transmission circuitry (not shown), the logic cireuits assisting greatly ~7~
. , ., .:~
in reducing the si2e and complexity of the data modulation circuits ~hat would have o~herwise been required. While the particular depicted transmitter operates at infrared frequencies, any medium for carrying a frequency modulated signal may be employed including sound waves, light waves or radio waves.
The receiver portion of the viewdata terminal comprises a charging stand 101 for the portable trans-mitter, a keyboard 102~ a frequency modulation receiver and terminal control unit 105, and a television 100.
The television 100 may alternatively receive television channels or frames of data informa~ion received over a telephone cable pair 104 connecting the viewdata terminal with a telephone central officeO Both types of information are selectably viewable on display screen 103 of television 100 .
When the terminal is employed for viewdata services, the user of transmitter 1 opera~es on/off switch 310. A seque~ce of data indicating that the transmi~ter has been turned on is transmitted over infrared lightwaves
FOR VOICE OR DATA
This invention relates -to ~requency modulation -transmitter circuit arrangements -For voice or data.
Cordless telephone s-ta-tion systems employing infrared transmission are known comprising a portable cordless transmitter with remote microphone and supervisory signalling capabili-ties. One such -transmitter is described in Anglikowski e-t al.~ U.S,Paten-t No, 4,221,932. The supervisory signalling is achieved by shifting the carrier ireqwency of the transmitted signal ~or indicating a low battery condi-tion and transmi.tter turno~'~'. There is no keyboard da-ta :lnput capability.
Al-ternatively, portable cordless transmitters are known for -transmi-tting keyboard en-tered data signals for controlling a ca-thode ray tube -television terminal. ~`or example, Richter et al., U.S.Patent No. 4, 091,272, discloses an infrared remote con-trolled command system for operating a -television receiver, heys of a keyboard are provided for selecting the television channel ox for controlling the volume level.
With the onse-t of viewda-ta services wherein a combination -telephone and television terminal may be prov.ided to telephone subscribers, it is believed desirable ~hat both voice and data be enterable ~rom the remote portable transmitter. The user O-e the transmitter would not have to be located in close proximity to -the viewdata terminal and would be able to remotely control its television and telephone functions.
In accordance wi-th the present invent~on the above stated problems and related problems of the prior art are alleviated by providing a circuit arrangement for use in a fre~uellcy modulatiorl tran~mitter ~or transmitting a firs-t, (voice~ signal and a second (data~
signal, the circuit arrangement comprising a data modulator and contro~ circuit for generating a modlllated 38 data ~ignal and a control signal indicating the presence 7~
o~ data, a signal mutlng switctl, responsive to -the control signal of the data modulator and control cireui-t, ~or mu-ting the first signal, and a gain swi-tch, responsive to the control signal o~ the da-ta moctulator and control circui-t, :eor at-tenua-ting the level o~ the modulated data signal. In a pre~erred embodimen-t o~
-the inven-tion the circui-t arrangement as a~oresaid wil:L
~orm part o~ a ~requency modulated -transmitter, advantageously o~ portable ~orm.
The transmitter comprises remote keyboard and mierophone capability and dual modes of use. In -the da-ta mode o~ use, earrier ~reqllency is only generated when the keyboard characters are depressed in order to conserve battery power. In the voice mode o:~ use, either voice or data may be transmi-tted, the data preemp-ting the voice.
~arrier ~requency is continuously generated in this mode.
A carrier eontrol circuit responsive to the selection o~
voiee or data mode provides -this carrier control ~ea-ture.
In the voiee mode of use, a data eontrol signal indieative o~ the presence o~ data is provided. The data eontrol signal eontrols the operation o~ a mierophone muting switeh and a frequency shi~t key gain switeh. I~
da-ta is present, the microphone is muted and, as a result, the data preempts the voice signal.
Spaee is another primary consideration in the design o~ a small portable transmitter. Aeeordingly, the transmitter eomprises a minimum number o~ eomponents provlding a maximum number o~ features. The primary eornponents o~ the present transmltter ~or providing a modulated data signal are two variable modulus eounters.
Tha ~irst eounter divides a eloek ~requeney either by one or another partieular modulus, its inp~-t being a binary bit da-ta ~tream. The seeoncl variable modulus eounter, responsive to the bina:ry bit stream divides the output o~
the ~irst eounter by the ~ame moduli oppositely. In this manner, an output signal is provicled at the input bit stream rate. This bit rate output, then, may be used to 38 provide a number o~ ~eatures a~ter passa~e-through a number s~
of particularizecl coun-ters.
Fo:r example, a data bit counter counts -the genera-ted data bits. In combination with a data selector circui-t ~or providing the binary data stream to the J~
counters, the data can be separated in-to words of a particular length. Another par-ti.cularized counter, a marker/data counter, inhibits the flow of data for the insertion of marker data before each data word. A frame counter provides information to an on~off control circuit for sending a particular number of frames of information to the receiver indicatiny that the transmitter has just been turned on or off.
Brief Deserip*ion of the Drawings FIG. 1 is a sehematie drawiny and pietorial representation of a viewdata serviees terminal eomprising the present frequeney modulation transmitter for voiee or data;
FIGS. 2, 3, and 4 are sehematie drawings and general bloek diagrams of one embodiment of the present frequeney modulation transmitter for voiee or data;
FIG. 5 is a key figure, demonstrating the relationships among FIGS. 2, 3, and 4;
FIG. 6 is a graphieal representation of one ~0 serial transmission ~eheme whieh may be employed in the present invention;
FIGS. 7, 8 and 9 are timing diagrams, illustrating thé operation of FIGS. 2, 3, and 4 and portraying waveforms at various points in the transmitter circuit over a duration of 21 time periods; and FIG. 10 is a key figure, demonstxating the relationships among FIGS. 7, 8, and 9.
Detailed Deseription Referring more partieularly to FIG. 1, there is shown a sehematie drawing and pietorial represen-tation of a terminal for providing viewdata services eomprising a transmitter 1 in aceordance with the present invention.
The transmitter 1 is portable and adapted to be hand-held.
It eomprises an on/off slide switeh 310, a mierophone ~02 and a keyboard 200. The transmitter also comprises integrated injeetion :Logic and infrared transmission circuitry (not shown), the logic cireuits assisting greatly ~7~
. , ., .:~
in reducing the si2e and complexity of the data modulation circuits ~hat would have o~herwise been required. While the particular depicted transmitter operates at infrared frequencies, any medium for carrying a frequency modulated signal may be employed including sound waves, light waves or radio waves.
The receiver portion of the viewdata terminal comprises a charging stand 101 for the portable trans-mitter, a keyboard 102~ a frequency modulation receiver and terminal control unit 105, and a television 100.
The television 100 may alternatively receive television channels or frames of data informa~ion received over a telephone cable pair 104 connecting the viewdata terminal with a telephone central officeO Both types of information are selectably viewable on display screen 103 of television 100 .
When the terminal is employed for viewdata services, the user of transmitter 1 opera~es on/off switch 310. A seque~ce of data indicating that the transmi~ter has been turned on is transmitted over infrared lightwaves
2 to receiver and terminal control unit 105.
One frequency modulation receiver which may be employed with the present ~ransmitter 1 is disclosed in Canadian Patent Application Serial No. 400,478, filed April 5, 1982 by D.H. Nash and D.H. YenO If lightwaves are employed, receiver 105 is assumed to comprise a lens system 105A for focusing direct and reflected lightwaves upon a photo transducer circuit 105B. The resultant electrical carrier frequency is then demodulated by a demodulator circuit 105C.
~ he transmitter 1 having transmitted a sequence of data codes signifying an l'on" condition, is now auto-matically placed in one of two operating modes, voice or data. In one particular embodiment, ~he data mode is entered first because, as it will be subsequently demonstrated, the data mode is a power-saving mode. Also, . . ~ 7~ 3 ~;
from a human Eac-tors s-tandpoint, it ls believed more likely that the -terminal operator will be inputtin~ command data information to the terminal at this -time.
In the data mode, the user may depress any one of the keyboard buttons or switch the transmitter off. Upon depressing a b-ltton, it will be subsequently described in great detail that -the user transm:its a sequence of frames of data relating to the button depressed either until a particular number of frames is transmitted or the button is released. Responsive to the receipt of the data, the viewdata receive terminal -typically displays the data on the screen 103 and performs the command entered.
The d~picted keyboard 200 portrays 21 bu-ttons or activatable commands. It may be implied therefrom that the number of possible commands is limited in comparison with keyboard 102 associated with the viewdata terminal. In actuality, the remote command ca~ability is only limited by the practicalities of the hand-held unit. The limited keyboard size, for example, may be overcome by providing for upper and lower case (shift~ operation, a diminishment of button size, or other means known in the art. The amount of transmitted data may be doubled by increasing the length of a data word by one bit. Accordingly, the subsequently described principles of the present invention may be employed regardless of the characteristics of the keyboard chosen.
Referring more particularly to key FIG. 5 and FIGS. 2, 3, and 4, a schematic drawing and block diagram of a transmitter in accordance with the present invention is shown. To show the interrela-tionships among FIGS. 2, 3, and 4, it is necessary to juxtaposition them in accordance with FIG. 5. Similar reference characters are used wherever possible to denote similar components already identified in FIG. 1. In addition, the first numeral oE the reference charac-ters employed in FIGS. 2, 3 and 4 refers to the number of the Eigure in which the item referred to ls located.
In FIG. 3, there is shown on/o~f switch 310 which may be a two position slide switch as is depic-ted in FIG. 1. There is also depicted a keep-on swi-tch 309.
These are connected to a source battery for the transmi-tter and are shown in their "on" state. Initially switch 309 is open and switch 310 is in the "off" position. When switch 310 is -turned on, a resistor and capacitor circuit (not shown) connected across the battery supply is activated which enables the on/off control circuit 215, in FIG. 2, to close keep-on switch 309. In this manner, power is provided to all logic circuits on a con-tinuous basis.
Referring now to FIG. 2, the activated on/off control circuit,215 provides a particular number of data words indicating that the transmi.-tter has been turned on to the data encoder circuit 201. The data is provided in parallel format to data latch circuit 202 where i-t is temporarily stored. Simultaneously, the data encoder circuit activates voice/data mode control circuit 216, which comprises memory indicating in which mode the transmitter is currently operating.
~ s previously discussed, the data mode is automatically assumed upon turn on. If it is desired to power up initially in the voice mode, the voice/data mode control circuit 216 may be so optioned. To change from the initial data mode to voi.ce or vice versa, one keyboard button may be set aside for this purpose, the information being simultaneously stored in voice/data mode control circuit 216 and transmitted to the receive terminal.
If the terminal is in the data mode, carrier control circuit 217 provides carrier con-trol signal L to close switch 311 only if data is present. Switch 311 provides power to carrier modulator and transmission circuitry 404, 408, 409 and 410 and voice preemphasis circui-t 403. As a result, carrier is only provided when data is presen-t for transmission in the data mode.
Alternatively, i~ the -terminal is in the voice mode, the carrier con-trol circuit 217 provides carrier . ~.. ~
control. signal L to main-tain switch 311 in a closed position so long as -the ~ransmitter is in the voice mode.
As battery power is continuously provoded to the carrier modu:Lator and tranSIniSSiOn circuitry 408, 409, and ~10, carrier is COIl tinuously transmitted in the voice mode.
To ensure that the receiver is prepared and recognizes the "on" condition of the transmitter, the code word indicating an "on" condition is transmitted a particular number of times. Control signal H, indicating the number of transmittals, is provided by frame counter 306 to on/off con~rol circuit 215. The operation of the frame counter 306 wi.ll be discussed in greater detail in the s~bsequent discussion of FIG. 3.
Similarly, when the transmitter is turned off, a particular number of codes i.ndicating on "off" condition i.s transmitted as follows. The user returns slide switch 310 to the "off" positi.on. Control circuit 215 provides "off"
codes continuously to data encoder 201 while switches 309 and 311 are maintained closed. When frame counter 306 provides indicator siynal H that the particular number of codes is reached, on/off control circuit 215 opens keep-on switch 309. Power is then cut off to all circuitry and carrier transmission ceasesO
Low battery detection circuit 212 operates as follows. Immediately after the transmitter is turned on, or after the transmitter has been in prolonged operation, the battery power reserve may fall below a particular acceptable level. In this eventl the low battery detection circuit provides an indication to low battery logic circuit 213. In the even-t that the transmitter has been just turned on or is idle, no data is being entere~ through keyboard 200. Accordi.ngly, the low battery logic circuit 213 desables the low battery code inhibit circuit 203, generates a unique low battery code, and causes its insertion in the data bit stream for transmission. ~lternatively, i:E data is being provided by data encoder circuit 201, the low bat-tery logic circuit 213 enables the low battery code inhibit circuit 203 for inhlbitin~ the transmission of the low bat-tery code until -the data has been transmi-tted. ~pon receiving the low battery code transmission, the receive terminal is able to provide an audible or visual warning to the user of a low battery condition. The user is -thereby encouraged -to recharge or replace the transmitter's batteries or operate the transmitter in its charging stand.
The Kl signal provided by flip bit generator 204 ]o is a locally generated signal intended to assist the terminal in recognizing breaks in data transmissi.on. ~ore a problem in infrared or ultrasonic than with radio transmission, t~ansmission can be broken by inadvertently covering the transmitting means. In the presen-t invention, a particular bit position of the transmitted data word is provided initially in a predetermined state and reversed or flipped in the next transmission of that wordO
Accordingly, at least two words are always transmitted. In the event of two intentional transmissions of the same data as when the user intentionally wishes to send two transmissions of the same character, the receive terminal is more likely to distinguish this event from a break in transmission. And, in the same manner, the receiver may not interpret an accidental momentary break in transmission as two deliberate character transmissions.
In one embodiment of transmitter 1, a five bit data word is provided by data encoder 201. Thirty-two possible code words comprise the twenty-one keyboard characters, the "on" and "off" codes, and the low bat-tery code. Of course, if more keyboard capahility is required, the data encoder capability must be increased in bi-t capacity. Besides the five data bits, a s-tart bit, -the reversible "flip" bi-t, and a parity bit may comprise an eight bit data word.
The data selection circuit or parallel to serial converter 301. of FIG. 3 provides the data word in serial form. Referring briefly to FIG. 6, there is shown one and ,.C~
-- 10. --one-half frames of data in serial torm. The eight bit data word comprises the start bit of 0 in position 0, fiYe bits of data, the "flip" bit in data bit position 6, and the parity bit in position 7 identifying either odd or even parity of the data bits and "flip" bit.
The flip bit generator 20~ provides on lead K1 the reversed "flip" bit to be placed in bit position 6.
This feature, however, may be implemented in any of the bit positions comprising the data word.
This "flip" bit may or may not be included in the calculation of odd or even pari-ty. In the depicted embodiment, it is assumed that the "flip" bi-t is included and the bit is provided to parity bit generation circuit 214 along with the five bits of data provided by data latch circuit 202 -through the low battery co~e inhibit circuit 203.
Referring now to FIG~ 3, the provision of a modulated data signal, in particular, a frequency shift keyed signal, and other features are now discussed in relation to the timing diagrams depicted in FIGS. 7, 8, and 9 and the serial transmission scheme depicted in FIGo 6.
Parallel to serial converter 301 of FIG~ 3 provides a complete data word in serial form to variable modulus counter 302 upon the depression of a button of keyboard 200. Depending upon the state of each bit positioned in the data word, the variable modulus counter 302 either divides a clock frequency by a first modulus M
or a second modulus N.
For example, the button representing "increase -the volume" of television 100 is pushed which may be represented by the five bit code 11010. The parallel to serial converter 301 may compose a data word in accordance with FIG. 6 of 01101001. The first 0 in the word is a start bit. The next six positions comprise the five positions of code and the "flip" bit of 0. The bit in bit position 7 assuming odd parity and including the "flip" bit in the parity calculation is a 1.
Accordingly, varlable modulus counter 302 divides the clock frequency by M upon recel~t of -the 0 start bit, by N upon receipt of the first two bits of data, by M upon the receipt of -the -third bit of data and so on.
In one embodiment, the clock fre~uency is 50kHz, M is 8 and N is 10. Upon receipt of a 0, a 6.25 kHz signal is generated. Upon receipt of a 1, a 5kHz signal is generated. Accordingly, a frequency shift key modulated data signal results which comprises time slots of binary data indicated by a particular frequency.
While other frequencies may be employed, the principles of the depicted embodiment require that the data frequencies are,selec-ted above the bandwidth of the human voice so that the voice and data may be simply sum~ed before modulation and transmission. Otherwise, the complexity of the transmitter and receiver circuitry would be greatly increased.
Variable modulus counter 303, responsive to the serial output A of the parallel to serial converter 301, divides the frequency shift key modulated data output B by N or M in opposition to the operation of the first variable modulus counter 302. In the particularly described embodiment~ a 6.25 kHz signal is always divided by 10 and a 5 kHz signal by 8. The result is a 625 Hz signal. This signal is an appropriate bit rate in accordance with the rate of data input from manually operated keyboard 200.
Data bit counter 304 counts the bits as the data is acted upon by the variable modulus counters. In the particularly described embodimen-t, a data word comprises eight bits. Accordingly, data bit counter 304 counts to binary eight, indicated by control signals D, E and F.
Control signals D, E and F, representing binary 8, are provided to the parallel to serial converter 301. Control signal F alone is provided to marker/data coun-ter 305.
There is a problem in that normal transmission of marker at tlle beginning and end of a string of data words may result in a loss of information transfer to the 5i,5~
receiver. Also, since data transmission is user activated and not continuous, synchronization of the receiver for da-ta demodulation must precede every data transmission.
Marker, which may be a series of eight 1 data bits, precedes every data word to ensure this synchronization in the receiver.
Referring brlefly to FIG. 6, there is shown a serial transmission scheme which resolves this problem.
Eight bits of marker data, comprising one word, is inserted before each data word of eight bi~s. The marker word and the data word together comprise one frame of data.
Marker/data counter 305, responsive to the control signal ,output F of the data bit counter 304, divides control signal output F by two resulting in inhibit signal G. Data inhibi-t signal C, provided to variable modulus counter 302, inhibits data flow so that marker may precede data.
Frame counter 306, responsive to the marker control output G of the marker/data counter 305, provides an indication of the number of frames of marker and data words transmitted. The frame counter 306 serves two functions. Firstl~, it is desirable to transmit at least two frames of data for data accuracy. Data is transmitted for at least two frames requiring 51.2 milliseconds even though a keyboard button may be depressed for as short a time as ten milliseconds. In the two frames, the t'flip"
bit and the parity bit change. As previously described, the receiver is thereby assisted in distinguishing between a break in transmission and a multiple transmission of the same data word. Secondly, it is desirable to count the number of frames of "on" or "off" codes in the turn on and turn off sequences. Accordingly, a frame counter control signal H, as previously described, is provided -to on/off control circuit 215 of FIG. 2.
At the same -time that data encoder 201 provides low battery logic circuit 213 wi-th a signal indicating the presence of data for transmission, that signal is also .~ "-. . , r 7~
provided to counter control and logic clearing circuit 312.
The counter con-trol and logic clearing circuit serves several functions.
It provides data control signal K to activate microphone muting switch 405 and FSK gain switch 406 shown in FIG. 4. As a result voice is preempted in the presence of data for transmission. It also maintains surveillance of the states of the various counters, including counters 302, 303, 304, 305 ancl 306 and is able to clear the counters for a new data stream 01- during transmitter turn on. Responsive to the control signal from data encoder 201, the counter control circuit 312 controls the operation of ca!rrier control circui~ 217 and data latch 202. In order to permit the receiver time to prepare 15 for the reception of data after carrier transmission is initiated, the counter control circuit 312 provides control signal I for delaying the transmlssion of FSK data signal s.
Referring now to FIG. 4, the voice input7 data preemption, and modulation circuitry are shown. In the voice mode of use, the voice preemphasis circuit 403 and the associated transmission and modulation circuits 404, 408, 409, and 410 are supplied power. When no data control signal K is present, voice or other signals provided through microphone 402 are preemphasized at preemphasis amplifier circuit 403. The preemphasized voice signal passes through summa~ion circuit 401 and is soft-clipped at limiter circuit 404. The output of limiter circuit 404 is modula-ted to a particular carrier frequency which should be selected to be much greater than the highest modulated data frequency. The output of the modulator is passed through a square wave to sine wave converter 409 and is provided to operate infrared driver amplifier 410 and optical transmission circuit 411 for providing infrared light waves 2.
In -the presence of data, however, -the voice input is preempted as follows. The data control signal K
7~
actlva-tes microphone muting switch 405 which may highly attenua-te or squelch altogether the voice input signal.
The l`SK modulated data signal J is summed at summation circuit 401 with the remaining voice signal.
In order to prevent over-modulation of the data signal, the FSK gain switch 40~tresponsive to the da-ta control signal ~, attenuates the output of the limiter circuit 404 through attenuation circuit 407. Modulation and infrared transmission proceed in the same manner as is practiced in the transmission of a voice signal alone.
Referring now to FIGS. 7, g, and 9 which are timing diagrams illustrating the operation of FIG's 2~ 3, and ~, it is useful to assume that -the transmitter is on ancl a button of keyboard 200 has been depressed, for example, the button representing "increase the volume" of television 100. The code to be initially transmitted for that button may be 01101001, of which data 11010 represents "increase the volume."
FIGS. 7, 8, and 9 show waveforms at various points in the transmitter circuit over a duration of twenty-one time periods of 1.6 milliseconds each after the keybo~rd button is depressed. Referring briefly to FIG. 10, a key figure, FIGS. 7, 8, and 9 should be placed side by si~e so that the waveforms representing a hutton push and waveforms labeled A-K appear to continue from left to right in increasing time periods from OT to 21T.
At OT, the button of keyboard 200 of FIG. 2 is depressed, data encoder 201 immediately responds by loading data latch 202 with the particular code for "increase the volume", 11010.
Whether the battery power level has just fallen below acceptable levels or not, because data is now present for transmission, the low battery code inhihit circuit 203 inhibits the provision of low battery code and -the Eive bit code is provided to parallel to serial converter 301 and parity generator circuit 214~
: ' '.
D
~ 15 -Meanwhile, the I<I signal is prees-tablished to be a O in -the initial transmission of a data word.
Accordingly, the KI signal is simul-taneously loaded into the sixth bit position by parallel to serial converter 301 and provided to parity generation circuit 214 of FIG. 2.
Assuming odd parity, parity generation circuit 21~, responsive to the KI signal and the five bit code, selects a parity bi-t, in this example, of 1. Parallel to serial converter 301 loads the parity bit into the seven-th lo bit position, inserts a start bit of O in position 0, and is now prepared to provide serial data signal A to variab:Le modulus counter 302. Referring to F~G.7, serial data signal A is shown between OT and 3T providing 011, the beginning of the code word.
Simultaneously with the but-ton push, counter control and logic clearing circuit 312 provides data control signal K to operate microphone muting switch 405 and FSK gain switch 407~
Carrier control circuit 217 initiates the transmission of carrier at OT. In the voice mode, carrier is continuously transmitted. After 3T, an arbitrary time period to allow the receiver to respond to the receipt of carrier in the data mode, control signal I is provided to AND gate 307 and FSK output data signal J is initiated.
Variable modulus counter 302, meanwhile, is in receipt of a data inhibit signal G provided through OR gate 313.
Data inhibit signal G causes counter 302 to initially provide marker data for comprising signal B.
Accordingly, despi-te the presence of data signal A, -the FSK
modulated data signal output B represents a string of 1 marker bits at 5kEIz, the 50 kEIz clock frequency ou~put of clock 308 divided by N or 10.
Variable modulus counter 303 recognizing that a stream of 1 bi-ts is being ac-ted upon by variable modulus counter 302 divides FS~< modulated da-ta signal B by M or 8.
Accordingly, bit rate signal C is provided at 625 Hz.
d~
Bit ra-te signal C is provided to da-ta bi-t counter 304 for counting the bits as they are transm1t-ted.
Output signals D, E, and F form a binary bit counter. For example, signals, F, E, and D at OT-lT read 000, a-t lT-2T
read 001, and at 2T-3T read 010. Once -the arbitrary time period OT-3T is complete, the receiver is prepared to receive da-ta. Counter control circuit 312 resets data bit counter 304, and output signals D, E, and F begin again to count bits. At the same time, control signal I, as previously mentioned, begins the flow of marker data signal J.
From 3T, shown in FIG. 7, to llT, shown in FIG. 8, the F, E, and D signals show a counting of data bits from 000 through lll. Data slgnal A indicates the code sequence 01101001. Because signal G, however, is low, data is inhibi-ted and marker signal B is pro~ided as the FSK modulated output signal J.
Data bit counter 304 output signal F, which indicates when four bits are transmitted is provided to marker data counter 305. At llT, output signal G, signal F
divided by two, of marker/data counter 305 now goes high indicating the transmittal of the eight marker bits. The output signal G is provided to variable modulus counter 302 to disable the inhibit of data.
Between llT and 12T, a binary O start bit from signal A is transmitted. The clock frequency is divided by B resulting in a 6.25 kHz square wave signal B between llT
and 12T. As signal I is still high, this signal also becomes FSK modulated data output signal J. Counter 303, responsive to a 0, divides the 6.25 kHz signal by lO
resulting in the same bit rate square wave C.
The five bit code word llOlO follows the start bit, forming FSK modulated data output signal J. Lastly, flip bit O and parity bit l complete the initial eight bit data word at l~T and l9T respectively, shown in FIG. 9.
The button is released at between 6T and 7T, shown in FIG. 7. It is known generally that a button may be depressed and released as quickly as ten milliseconds.
On the other hand, the button may be held in a depressed state far longer. Accordingly, consideration of two factors becomes relevant; the anticipated bit rate of input from a transmitte:r user and, on the other hand, the desirability of providing secure and reliable data transmission.
In the particular discussed embodiment, the bit rate of 625 ~Iz represents a norma:l expected bit rate for a user operable keyboard. Additionally, despite the potentially short button push of ten milliseconds, at least two frames of a data word, requiring about 50 milliseconds, are transmitted~ In other embodiments, these factors may be weighed differently resulting in different allocations of marker data, a data word of a different length or other design changes known in the art~
Marker/data counter 305 output signal G is provided to frame counter 306 which assures that a particular number of frames of data or a sequence of frames Of data for on/off codes is transmitted. At l9T, output signal H of frame counter 306 goes high for the first time indicating that one complete frame of marker and data words has been transmitted.
After l9T, marker/data counter 305 output signal G goes low again inhibiting the flow of data. Signals and J after l9T again represent the flow of marker. At 27T, not shown, a new data word is transmitted comprising the same information in bit positions 0-5, but a "flip" bit of 1 in bit position 6, and a parity bit of 0 in bit position 7.
In the event that the user con-tinues to depress the button aEter two frames of data are -transmit-ted, data transmission may continue until the button is released. On the o-ther hand, after a quick bu-tton release, data transmission should continue until a complete data word has been transmi-t-ted and marker is about to begin again.
One frequency modulation receiver which may be employed with the present ~ransmitter 1 is disclosed in Canadian Patent Application Serial No. 400,478, filed April 5, 1982 by D.H. Nash and D.H. YenO If lightwaves are employed, receiver 105 is assumed to comprise a lens system 105A for focusing direct and reflected lightwaves upon a photo transducer circuit 105B. The resultant electrical carrier frequency is then demodulated by a demodulator circuit 105C.
~ he transmitter 1 having transmitted a sequence of data codes signifying an l'on" condition, is now auto-matically placed in one of two operating modes, voice or data. In one particular embodiment, ~he data mode is entered first because, as it will be subsequently demonstrated, the data mode is a power-saving mode. Also, . . ~ 7~ 3 ~;
from a human Eac-tors s-tandpoint, it ls believed more likely that the -terminal operator will be inputtin~ command data information to the terminal at this -time.
In the data mode, the user may depress any one of the keyboard buttons or switch the transmitter off. Upon depressing a b-ltton, it will be subsequently described in great detail that -the user transm:its a sequence of frames of data relating to the button depressed either until a particular number of frames is transmitted or the button is released. Responsive to the receipt of the data, the viewdata receive terminal -typically displays the data on the screen 103 and performs the command entered.
The d~picted keyboard 200 portrays 21 bu-ttons or activatable commands. It may be implied therefrom that the number of possible commands is limited in comparison with keyboard 102 associated with the viewdata terminal. In actuality, the remote command ca~ability is only limited by the practicalities of the hand-held unit. The limited keyboard size, for example, may be overcome by providing for upper and lower case (shift~ operation, a diminishment of button size, or other means known in the art. The amount of transmitted data may be doubled by increasing the length of a data word by one bit. Accordingly, the subsequently described principles of the present invention may be employed regardless of the characteristics of the keyboard chosen.
Referring more particularly to key FIG. 5 and FIGS. 2, 3, and 4, a schematic drawing and block diagram of a transmitter in accordance with the present invention is shown. To show the interrela-tionships among FIGS. 2, 3, and 4, it is necessary to juxtaposition them in accordance with FIG. 5. Similar reference characters are used wherever possible to denote similar components already identified in FIG. 1. In addition, the first numeral oE the reference charac-ters employed in FIGS. 2, 3 and 4 refers to the number of the Eigure in which the item referred to ls located.
In FIG. 3, there is shown on/o~f switch 310 which may be a two position slide switch as is depic-ted in FIG. 1. There is also depicted a keep-on swi-tch 309.
These are connected to a source battery for the transmi-tter and are shown in their "on" state. Initially switch 309 is open and switch 310 is in the "off" position. When switch 310 is -turned on, a resistor and capacitor circuit (not shown) connected across the battery supply is activated which enables the on/off control circuit 215, in FIG. 2, to close keep-on switch 309. In this manner, power is provided to all logic circuits on a con-tinuous basis.
Referring now to FIG. 2, the activated on/off control circuit,215 provides a particular number of data words indicating that the transmi.-tter has been turned on to the data encoder circuit 201. The data is provided in parallel format to data latch circuit 202 where i-t is temporarily stored. Simultaneously, the data encoder circuit activates voice/data mode control circuit 216, which comprises memory indicating in which mode the transmitter is currently operating.
~ s previously discussed, the data mode is automatically assumed upon turn on. If it is desired to power up initially in the voice mode, the voice/data mode control circuit 216 may be so optioned. To change from the initial data mode to voi.ce or vice versa, one keyboard button may be set aside for this purpose, the information being simultaneously stored in voice/data mode control circuit 216 and transmitted to the receive terminal.
If the terminal is in the data mode, carrier control circuit 217 provides carrier con-trol signal L to close switch 311 only if data is present. Switch 311 provides power to carrier modulator and transmission circuitry 404, 408, 409 and 410 and voice preemphasis circui-t 403. As a result, carrier is only provided when data is presen-t for transmission in the data mode.
Alternatively, i~ the -terminal is in the voice mode, the carrier con-trol circuit 217 provides carrier . ~.. ~
control. signal L to main-tain switch 311 in a closed position so long as -the ~ransmitter is in the voice mode.
As battery power is continuously provoded to the carrier modu:Lator and tranSIniSSiOn circuitry 408, 409, and ~10, carrier is COIl tinuously transmitted in the voice mode.
To ensure that the receiver is prepared and recognizes the "on" condition of the transmitter, the code word indicating an "on" condition is transmitted a particular number of times. Control signal H, indicating the number of transmittals, is provided by frame counter 306 to on/off con~rol circuit 215. The operation of the frame counter 306 wi.ll be discussed in greater detail in the s~bsequent discussion of FIG. 3.
Similarly, when the transmitter is turned off, a particular number of codes i.ndicating on "off" condition i.s transmitted as follows. The user returns slide switch 310 to the "off" positi.on. Control circuit 215 provides "off"
codes continuously to data encoder 201 while switches 309 and 311 are maintained closed. When frame counter 306 provides indicator siynal H that the particular number of codes is reached, on/off control circuit 215 opens keep-on switch 309. Power is then cut off to all circuitry and carrier transmission ceasesO
Low battery detection circuit 212 operates as follows. Immediately after the transmitter is turned on, or after the transmitter has been in prolonged operation, the battery power reserve may fall below a particular acceptable level. In this eventl the low battery detection circuit provides an indication to low battery logic circuit 213. In the even-t that the transmitter has been just turned on or is idle, no data is being entere~ through keyboard 200. Accordi.ngly, the low battery logic circuit 213 desables the low battery code inhibit circuit 203, generates a unique low battery code, and causes its insertion in the data bit stream for transmission. ~lternatively, i:E data is being provided by data encoder circuit 201, the low bat-tery logic circuit 213 enables the low battery code inhibit circuit 203 for inhlbitin~ the transmission of the low bat-tery code until -the data has been transmi-tted. ~pon receiving the low battery code transmission, the receive terminal is able to provide an audible or visual warning to the user of a low battery condition. The user is -thereby encouraged -to recharge or replace the transmitter's batteries or operate the transmitter in its charging stand.
The Kl signal provided by flip bit generator 204 ]o is a locally generated signal intended to assist the terminal in recognizing breaks in data transmissi.on. ~ore a problem in infrared or ultrasonic than with radio transmission, t~ansmission can be broken by inadvertently covering the transmitting means. In the presen-t invention, a particular bit position of the transmitted data word is provided initially in a predetermined state and reversed or flipped in the next transmission of that wordO
Accordingly, at least two words are always transmitted. In the event of two intentional transmissions of the same data as when the user intentionally wishes to send two transmissions of the same character, the receive terminal is more likely to distinguish this event from a break in transmission. And, in the same manner, the receiver may not interpret an accidental momentary break in transmission as two deliberate character transmissions.
In one embodiment of transmitter 1, a five bit data word is provided by data encoder 201. Thirty-two possible code words comprise the twenty-one keyboard characters, the "on" and "off" codes, and the low bat-tery code. Of course, if more keyboard capahility is required, the data encoder capability must be increased in bi-t capacity. Besides the five data bits, a s-tart bit, -the reversible "flip" bi-t, and a parity bit may comprise an eight bit data word.
The data selection circuit or parallel to serial converter 301. of FIG. 3 provides the data word in serial form. Referring briefly to FIG. 6, there is shown one and ,.C~
-- 10. --one-half frames of data in serial torm. The eight bit data word comprises the start bit of 0 in position 0, fiYe bits of data, the "flip" bit in data bit position 6, and the parity bit in position 7 identifying either odd or even parity of the data bits and "flip" bit.
The flip bit generator 20~ provides on lead K1 the reversed "flip" bit to be placed in bit position 6.
This feature, however, may be implemented in any of the bit positions comprising the data word.
This "flip" bit may or may not be included in the calculation of odd or even pari-ty. In the depicted embodiment, it is assumed that the "flip" bi-t is included and the bit is provided to parity bit generation circuit 214 along with the five bits of data provided by data latch circuit 202 -through the low battery co~e inhibit circuit 203.
Referring now to FIG~ 3, the provision of a modulated data signal, in particular, a frequency shift keyed signal, and other features are now discussed in relation to the timing diagrams depicted in FIGS. 7, 8, and 9 and the serial transmission scheme depicted in FIGo 6.
Parallel to serial converter 301 of FIG~ 3 provides a complete data word in serial form to variable modulus counter 302 upon the depression of a button of keyboard 200. Depending upon the state of each bit positioned in the data word, the variable modulus counter 302 either divides a clock frequency by a first modulus M
or a second modulus N.
For example, the button representing "increase -the volume" of television 100 is pushed which may be represented by the five bit code 11010. The parallel to serial converter 301 may compose a data word in accordance with FIG. 6 of 01101001. The first 0 in the word is a start bit. The next six positions comprise the five positions of code and the "flip" bit of 0. The bit in bit position 7 assuming odd parity and including the "flip" bit in the parity calculation is a 1.
Accordingly, varlable modulus counter 302 divides the clock frequency by M upon recel~t of -the 0 start bit, by N upon receipt of the first two bits of data, by M upon the receipt of -the -third bit of data and so on.
In one embodiment, the clock fre~uency is 50kHz, M is 8 and N is 10. Upon receipt of a 0, a 6.25 kHz signal is generated. Upon receipt of a 1, a 5kHz signal is generated. Accordingly, a frequency shift key modulated data signal results which comprises time slots of binary data indicated by a particular frequency.
While other frequencies may be employed, the principles of the depicted embodiment require that the data frequencies are,selec-ted above the bandwidth of the human voice so that the voice and data may be simply sum~ed before modulation and transmission. Otherwise, the complexity of the transmitter and receiver circuitry would be greatly increased.
Variable modulus counter 303, responsive to the serial output A of the parallel to serial converter 301, divides the frequency shift key modulated data output B by N or M in opposition to the operation of the first variable modulus counter 302. In the particularly described embodiment~ a 6.25 kHz signal is always divided by 10 and a 5 kHz signal by 8. The result is a 625 Hz signal. This signal is an appropriate bit rate in accordance with the rate of data input from manually operated keyboard 200.
Data bit counter 304 counts the bits as the data is acted upon by the variable modulus counters. In the particularly described embodimen-t, a data word comprises eight bits. Accordingly, data bit counter 304 counts to binary eight, indicated by control signals D, E and F.
Control signals D, E and F, representing binary 8, are provided to the parallel to serial converter 301. Control signal F alone is provided to marker/data coun-ter 305.
There is a problem in that normal transmission of marker at tlle beginning and end of a string of data words may result in a loss of information transfer to the 5i,5~
receiver. Also, since data transmission is user activated and not continuous, synchronization of the receiver for da-ta demodulation must precede every data transmission.
Marker, which may be a series of eight 1 data bits, precedes every data word to ensure this synchronization in the receiver.
Referring brlefly to FIG. 6, there is shown a serial transmission scheme which resolves this problem.
Eight bits of marker data, comprising one word, is inserted before each data word of eight bi~s. The marker word and the data word together comprise one frame of data.
Marker/data counter 305, responsive to the control signal ,output F of the data bit counter 304, divides control signal output F by two resulting in inhibit signal G. Data inhibi-t signal C, provided to variable modulus counter 302, inhibits data flow so that marker may precede data.
Frame counter 306, responsive to the marker control output G of the marker/data counter 305, provides an indication of the number of frames of marker and data words transmitted. The frame counter 306 serves two functions. Firstl~, it is desirable to transmit at least two frames of data for data accuracy. Data is transmitted for at least two frames requiring 51.2 milliseconds even though a keyboard button may be depressed for as short a time as ten milliseconds. In the two frames, the t'flip"
bit and the parity bit change. As previously described, the receiver is thereby assisted in distinguishing between a break in transmission and a multiple transmission of the same data word. Secondly, it is desirable to count the number of frames of "on" or "off" codes in the turn on and turn off sequences. Accordingly, a frame counter control signal H, as previously described, is provided -to on/off control circuit 215 of FIG. 2.
At the same -time that data encoder 201 provides low battery logic circuit 213 wi-th a signal indicating the presence of data for transmission, that signal is also .~ "-. . , r 7~
provided to counter control and logic clearing circuit 312.
The counter con-trol and logic clearing circuit serves several functions.
It provides data control signal K to activate microphone muting switch 405 and FSK gain switch 406 shown in FIG. 4. As a result voice is preempted in the presence of data for transmission. It also maintains surveillance of the states of the various counters, including counters 302, 303, 304, 305 ancl 306 and is able to clear the counters for a new data stream 01- during transmitter turn on. Responsive to the control signal from data encoder 201, the counter control circuit 312 controls the operation of ca!rrier control circui~ 217 and data latch 202. In order to permit the receiver time to prepare 15 for the reception of data after carrier transmission is initiated, the counter control circuit 312 provides control signal I for delaying the transmlssion of FSK data signal s.
Referring now to FIG. 4, the voice input7 data preemption, and modulation circuitry are shown. In the voice mode of use, the voice preemphasis circuit 403 and the associated transmission and modulation circuits 404, 408, 409, and 410 are supplied power. When no data control signal K is present, voice or other signals provided through microphone 402 are preemphasized at preemphasis amplifier circuit 403. The preemphasized voice signal passes through summa~ion circuit 401 and is soft-clipped at limiter circuit 404. The output of limiter circuit 404 is modula-ted to a particular carrier frequency which should be selected to be much greater than the highest modulated data frequency. The output of the modulator is passed through a square wave to sine wave converter 409 and is provided to operate infrared driver amplifier 410 and optical transmission circuit 411 for providing infrared light waves 2.
In -the presence of data, however, -the voice input is preempted as follows. The data control signal K
7~
actlva-tes microphone muting switch 405 which may highly attenua-te or squelch altogether the voice input signal.
The l`SK modulated data signal J is summed at summation circuit 401 with the remaining voice signal.
In order to prevent over-modulation of the data signal, the FSK gain switch 40~tresponsive to the da-ta control signal ~, attenuates the output of the limiter circuit 404 through attenuation circuit 407. Modulation and infrared transmission proceed in the same manner as is practiced in the transmission of a voice signal alone.
Referring now to FIGS. 7, g, and 9 which are timing diagrams illustrating the operation of FIG's 2~ 3, and ~, it is useful to assume that -the transmitter is on ancl a button of keyboard 200 has been depressed, for example, the button representing "increase the volume" of television 100. The code to be initially transmitted for that button may be 01101001, of which data 11010 represents "increase the volume."
FIGS. 7, 8, and 9 show waveforms at various points in the transmitter circuit over a duration of twenty-one time periods of 1.6 milliseconds each after the keybo~rd button is depressed. Referring briefly to FIG. 10, a key figure, FIGS. 7, 8, and 9 should be placed side by si~e so that the waveforms representing a hutton push and waveforms labeled A-K appear to continue from left to right in increasing time periods from OT to 21T.
At OT, the button of keyboard 200 of FIG. 2 is depressed, data encoder 201 immediately responds by loading data latch 202 with the particular code for "increase the volume", 11010.
Whether the battery power level has just fallen below acceptable levels or not, because data is now present for transmission, the low battery code inhihit circuit 203 inhibits the provision of low battery code and -the Eive bit code is provided to parallel to serial converter 301 and parity generator circuit 214~
: ' '.
D
~ 15 -Meanwhile, the I<I signal is prees-tablished to be a O in -the initial transmission of a data word.
Accordingly, the KI signal is simul-taneously loaded into the sixth bit position by parallel to serial converter 301 and provided to parity generation circuit 214 of FIG. 2.
Assuming odd parity, parity generation circuit 21~, responsive to the KI signal and the five bit code, selects a parity bi-t, in this example, of 1. Parallel to serial converter 301 loads the parity bit into the seven-th lo bit position, inserts a start bit of O in position 0, and is now prepared to provide serial data signal A to variab:Le modulus counter 302. Referring to F~G.7, serial data signal A is shown between OT and 3T providing 011, the beginning of the code word.
Simultaneously with the but-ton push, counter control and logic clearing circuit 312 provides data control signal K to operate microphone muting switch 405 and FSK gain switch 407~
Carrier control circuit 217 initiates the transmission of carrier at OT. In the voice mode, carrier is continuously transmitted. After 3T, an arbitrary time period to allow the receiver to respond to the receipt of carrier in the data mode, control signal I is provided to AND gate 307 and FSK output data signal J is initiated.
Variable modulus counter 302, meanwhile, is in receipt of a data inhibit signal G provided through OR gate 313.
Data inhibit signal G causes counter 302 to initially provide marker data for comprising signal B.
Accordingly, despi-te the presence of data signal A, -the FSK
modulated data signal output B represents a string of 1 marker bits at 5kEIz, the 50 kEIz clock frequency ou~put of clock 308 divided by N or 10.
Variable modulus counter 303 recognizing that a stream of 1 bi-ts is being ac-ted upon by variable modulus counter 302 divides FS~< modulated da-ta signal B by M or 8.
Accordingly, bit rate signal C is provided at 625 Hz.
d~
Bit ra-te signal C is provided to da-ta bi-t counter 304 for counting the bits as they are transm1t-ted.
Output signals D, E, and F form a binary bit counter. For example, signals, F, E, and D at OT-lT read 000, a-t lT-2T
read 001, and at 2T-3T read 010. Once -the arbitrary time period OT-3T is complete, the receiver is prepared to receive da-ta. Counter control circuit 312 resets data bit counter 304, and output signals D, E, and F begin again to count bits. At the same time, control signal I, as previously mentioned, begins the flow of marker data signal J.
From 3T, shown in FIG. 7, to llT, shown in FIG. 8, the F, E, and D signals show a counting of data bits from 000 through lll. Data slgnal A indicates the code sequence 01101001. Because signal G, however, is low, data is inhibi-ted and marker signal B is pro~ided as the FSK modulated output signal J.
Data bit counter 304 output signal F, which indicates when four bits are transmitted is provided to marker data counter 305. At llT, output signal G, signal F
divided by two, of marker/data counter 305 now goes high indicating the transmittal of the eight marker bits. The output signal G is provided to variable modulus counter 302 to disable the inhibit of data.
Between llT and 12T, a binary O start bit from signal A is transmitted. The clock frequency is divided by B resulting in a 6.25 kHz square wave signal B between llT
and 12T. As signal I is still high, this signal also becomes FSK modulated data output signal J. Counter 303, responsive to a 0, divides the 6.25 kHz signal by lO
resulting in the same bit rate square wave C.
The five bit code word llOlO follows the start bit, forming FSK modulated data output signal J. Lastly, flip bit O and parity bit l complete the initial eight bit data word at l~T and l9T respectively, shown in FIG. 9.
The button is released at between 6T and 7T, shown in FIG. 7. It is known generally that a button may be depressed and released as quickly as ten milliseconds.
On the other hand, the button may be held in a depressed state far longer. Accordingly, consideration of two factors becomes relevant; the anticipated bit rate of input from a transmitte:r user and, on the other hand, the desirability of providing secure and reliable data transmission.
In the particular discussed embodiment, the bit rate of 625 ~Iz represents a norma:l expected bit rate for a user operable keyboard. Additionally, despite the potentially short button push of ten milliseconds, at least two frames of a data word, requiring about 50 milliseconds, are transmitted~ In other embodiments, these factors may be weighed differently resulting in different allocations of marker data, a data word of a different length or other design changes known in the art~
Marker/data counter 305 output signal G is provided to frame counter 306 which assures that a particular number of frames of data or a sequence of frames Of data for on/off codes is transmitted. At l9T, output signal H of frame counter 306 goes high for the first time indicating that one complete frame of marker and data words has been transmitted.
After l9T, marker/data counter 305 output signal G goes low again inhibiting the flow of data. Signals and J after l9T again represent the flow of marker. At 27T, not shown, a new data word is transmitted comprising the same information in bit positions 0-5, but a "flip" bit of 1 in bit position 6, and a parity bit of 0 in bit position 7.
In the event that the user con-tinues to depress the button aEter two frames of data are -transmit-ted, data transmission may continue until the button is released. On the o-ther hand, after a quick bu-tton release, data transmission should continue until a complete data word has been transmi-t-ted and marker is about to begin again.
Claims (19)
1. A circuit arrangement for use in a frequency modulation transmitter for transmitting a first signal or a second data signal, CHARACTERISED BY a data modulator and control circuit (312,302,307) for generating a modulated data signal (J) and a control signal (K) indicating the presence of data, a signal muting switch (405), responsive to the control signal of the data modulator and control circuit, for muting the first signal, and a gain switch (406), responsive to the control signal of the data modulator and control circuit, for attenuating the level of the modulated data signal.
2. A circuit arrangement as claimed in claim 1 further CHARACTERISED BY a summation circuit (401), for summing the first signal and the modulated data signal and a limiter circuit (404), responsive to the summation circuit, for soft clipping the output of the summation circuit.
3. A circuit arrangement as claimed in claim 1 CHARACTERISED IN THAT the data modulator and control circuit is effective for generating a frequency shift keyed data signal (J).
4. A circuit arrangement as claimed in claim 3 CHARACTERISED BY a frequency shift keyed signal generator circuit comprising: a first variable modulus counter (302) for dividing a clock frequency by a particular first or second modulus (M or N), the applied input (A) being a binary zero or one data signal respectively, the output being a frequency shift keyed signal (B), and a second variable modulus counter (303), responsive to the applied input signal (A) and the frequency shift keyed output signal (B) of the first variable modulus counter (302), for dividing the frequency shift keyed output signal by the predetermined second or first modulus (N or M), the output (C) being at the bit rate of the applied input signal (A).
5. A circuit arrangement as claimed in claim 4 further CHARACTERIZED IN THAT the frequency shift keyed signal generator circuit comprises a data bit counter (304), responsive to the output of the second variable modulus counter (303), for dividing the output of the second variable modulus counter by a particular binary quantity of data bits.
6. A circuit arrangement as claimed in claim 5 further CHARACTERISED IN THAT the frequency shift keyed signal generator circuit comprises a data selector circuit(301), for inserting a flip bit in the applied binary data input (A), the flip bit for assisting a receive terminal to distinguish between a break in data transmission and a multiple transmission of the same data.
7. A circuit arrangement as claimed in claim 6 further CHARACTERISED IN THAT the data selector circuit (301) additionally inserts a parity bit, dependent on the flip bit, in the applied binary data input (A).
8. A circuit arrangement as claimed in claim 5 further CHARACTERISED IN THAT the frequency shift keyed signal generator circuit comprises a low battery indicating circuit (203,212,213,301), responsive to a control signal indicating a low battery condition, for inserting a particular code for the low battery condition in the applied binary data input.
9. A circuit arrangement as claimed in claim 8 further CHARACTERISED IN THAT the low battery indicating circuit comprises a low battery code inhibit circuit (203), responsive to a data signal, for inhibiting the insertion of the particular low battery code in the presence of the data signal,
10, A circuit arrangement as claimed in claim 5 further CMARACTERISED IN THAT the frequency shift keyed signal generator circuit comprises a data selector circuit (301) for inserting a flip bit having a particular periodic location in the applied binary data input (A).
11. A circuit arrangement as claimed in claim 5 further CHARACTERISED IN THAT the frequency shift keyed signal generator circuit comprises a marker data counter responsive to the data bit counter, for providing a control signal (G) to the first variable modulus counter, the control signal regulating the provision of marker data.
12. A circuit arrangement as claimed in claim 11 further CHARACTERISED IN THAT the frequency shift keyed signal generator circuit comprises a frame counter responsive to the marker/data counter.
13. A portable frequency modulation transmitter CHARACTERISED BY a circuit arrangement as claimed in claim 1, further CHARACTERISED IN THAT said circuit arrangement comprises: a keyboard for data input, a microphone for voice input, and a modulator for modulating the data above the voice.
14. A portable frequency modulation transmitter for data or voice, CHARACTERISED BY
a keyboard for data input, a microphone for voice input, and a modulator for modulating the input data to first and second frequency levels above voice frequency level signals, and a data preemption circuit for pre-empting the transmission of voice frequency level signals in the presence of a data signal for transmission, the data preemption circuit comprising a control circuit for providing a control signal (K), the control signal actuating switching circuitry for attenuating the voice frequency level signals and switching circuitry for attenuating the data signal.
a keyboard for data input, a microphone for voice input, and a modulator for modulating the input data to first and second frequency levels above voice frequency level signals, and a data preemption circuit for pre-empting the transmission of voice frequency level signals in the presence of a data signal for transmission, the data preemption circuit comprising a control circuit for providing a control signal (K), the control signal actuating switching circuitry for attenuating the voice frequency level signals and switching circuitry for attenuating the data signal.
15. A portable frequency modulation transmitter for data or voice CHARACTERISED BY
a data modulator and control circuit for generating a modulated data signal (J) and a control signal (K) indicating the presence of data, a gain switch, responsive to the control signal of the data modulator and control circuit, for attenuating the level of the modulated data signal, and a voice/data mode control circuit responsive to the presence of data, the voice/data mode control circuit providing a first mode of use for voice transmission wherein carrier is continuously provided and a second mode of use wherein carrier is provided only during the presence of data for transmission, the voice/data mode control circuit storing mode of use data, and a carrier control circuit responsive to the data modulator and control circuit and the voice/data mode control circuit providing a carrier control signal (L) for regulating the provision of carrier.
a data modulator and control circuit for generating a modulated data signal (J) and a control signal (K) indicating the presence of data, a gain switch, responsive to the control signal of the data modulator and control circuit, for attenuating the level of the modulated data signal, and a voice/data mode control circuit responsive to the presence of data, the voice/data mode control circuit providing a first mode of use for voice transmission wherein carrier is continuously provided and a second mode of use wherein carrier is provided only during the presence of data for transmission, the voice/data mode control circuit storing mode of use data, and a carrier control circuit responsive to the data modulator and control circuit and the voice/data mode control circuit providing a carrier control signal (L) for regulating the provision of carrier.
16. In a frequency modulation transmitter for transmitting a first or a second signal, a preemption circuit for preempting the first signal, CHARACTERISED BY
means for generating a second signal and a control signal indicating the presence of the second signal, means, responsive to the control signal, for muting the first signal, means for summing the second signal and the output of the signal muting means, and means, responsive to the control signal, for attenuating the output of the summing means.
means for generating a second signal and a control signal indicating the presence of the second signal, means, responsive to the control signal, for muting the first signal, means for summing the second signal and the output of the signal muting means, and means, responsive to the control signal, for attenuating the output of the summing means.
17. In a frequency modulation transmitter for transmitting a first signal or a second data signal, means for controlling the provision of carrier, the transmitted signal modulating the carrier CHARACTERISED BY
a data modulator and control circuit for generating a modulated data signal (J) and a control signal (K) indicating the presence of data, a gain switch, responsive to the control signal of the data modulator and control circuit, for attenuating the level of the modulated data signal, and carrier control means responsive to the data modulator and control circuit and a mode control circuit for controlling the provision of carrier, the mode control circuit storing a selection of a first or second trans-mission mode and providing a carrier control signal (L) for inhibiting the provision of carrier when the second transmission mode is selected except during the presence of the second data signal for transmission and, permitting the provision of carrier when the first transmission mode is selected.
a data modulator and control circuit for generating a modulated data signal (J) and a control signal (K) indicating the presence of data, a gain switch, responsive to the control signal of the data modulator and control circuit, for attenuating the level of the modulated data signal, and carrier control means responsive to the data modulator and control circuit and a mode control circuit for controlling the provision of carrier, the mode control circuit storing a selection of a first or second trans-mission mode and providing a carrier control signal (L) for inhibiting the provision of carrier when the second transmission mode is selected except during the presence of the second data signal for transmission and, permitting the provision of carrier when the first transmission mode is selected.
18. A frequency modulation transmitter for data or voice CHARACTERISED BY
a frequency shift key modulator for modulating input data to first and second frequency levels above voice frequency level signals, a data preemption circuit for preempting the transmission of the voice frequency level signals in the presence of the input data for transmission, the data preemption circuit comprising a control circuit responsive to the presence of the input data, the control circuit providing a control signal (K) indicating the presence of data, a signal muting switch, responsive to the control signal of the control circuit, for muting the voice frequency level signals, and a frequency shift keyed signal gain switch, responsive to the control signal of the control circuit, for attenuating the output signal level of the frequency shift key modulator.
a frequency shift key modulator for modulating input data to first and second frequency levels above voice frequency level signals, a data preemption circuit for preempting the transmission of the voice frequency level signals in the presence of the input data for transmission, the data preemption circuit comprising a control circuit responsive to the presence of the input data, the control circuit providing a control signal (K) indicating the presence of data, a signal muting switch, responsive to the control signal of the control circuit, for muting the voice frequency level signals, and a frequency shift keyed signal gain switch, responsive to the control signal of the control circuit, for attenuating the output signal level of the frequency shift key modulator.
19. A frequency modulation transmitter for data or voice as recited in claim 18 , further CHARACTERISED IN THAT
the first and second frequency levels are a quotient output of a clock frequency input to the frequency shift key modulator, the first and second frequency levels being further dividable, and dividing means being a variable modulus counter.
the first and second frequency levels are a quotient output of a clock frequency input to the frequency shift key modulator, the first and second frequency levels being further dividable, and dividing means being a variable modulus counter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US251,258 | 1981-04-06 | ||
| US06/251,258 US4418416A (en) | 1981-04-06 | 1981-04-06 | Frequency modulation transmitter for voice or data |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1197559A true CA1197559A (en) | 1985-12-03 |
Family
ID=22951157
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000400469A Expired CA1197559A (en) | 1981-04-06 | 1982-04-05 | Frequency modulation transmitter circuit arrangements for voice or data |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4418416A (en) |
| JP (1) | JPS57193166A (en) |
| BE (1) | BE892759A (en) |
| CA (1) | CA1197559A (en) |
| DE (1) | DE3212540A1 (en) |
| FR (1) | FR2503485B1 (en) |
| GB (1) | GB2097633B (en) |
| IT (1) | IT1150532B (en) |
| NL (1) | NL8201448A (en) |
| SE (1) | SE452831B (en) |
Families Citing this family (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1175964A (en) * | 1982-02-22 | 1984-10-09 | John A. Barsellotti | Two wire voice and data subscriber loop |
| US4544923A (en) * | 1982-12-22 | 1985-10-01 | Rca Corporation | Microprocessor self-turn-off arrangement for a consumer instrument |
| US4544924A (en) * | 1982-12-22 | 1985-10-01 | Rca Corporation | On-off arrangement in a microprocessor controlled remote transmitter for a consumer instrument |
| US4608699A (en) * | 1982-12-27 | 1986-08-26 | Motorola, Inc. | Simulcast transmission system |
| US4721955A (en) * | 1983-04-22 | 1988-01-26 | Motorola, Inc. | Paging universal remote control system |
| US4758833A (en) * | 1983-04-22 | 1988-07-19 | Motorola, Inc. | Paging universal remote control decoder |
| US4701758A (en) * | 1983-08-05 | 1987-10-20 | Motorola, Inc. | Individual simulcast transmitter remote control system encoder |
| US4772887A (en) * | 1983-08-05 | 1988-09-20 | Motorola, Inc. | Individual simulcast station control decoder |
| JPS6064272A (en) * | 1983-09-19 | 1985-04-12 | Nissan Motor Co Ltd | Radio type on-vehicle load control apparatus |
| JPS61196080A (en) * | 1985-02-21 | 1986-08-30 | 日産自動車株式会社 | Wireless user discrimination apparatus |
| FR2580879A1 (en) * | 1985-04-23 | 1986-10-24 | Mundi Electronic Anstalt | Portable radio receiver of very high performance and with multiple preselected stations. |
| JPS6238035A (en) * | 1985-08-12 | 1987-02-19 | Nissan Motor Co Ltd | Thin plate type portable device |
| JPS6278379A (en) * | 1985-09-30 | 1987-04-10 | 日産自動車株式会社 | Locking and unlocking control apparatus for vehicle |
| JPH0625503B2 (en) * | 1986-06-20 | 1994-04-06 | 日産自動車株式会社 | Unlock control device |
| US4723268A (en) * | 1986-09-22 | 1988-02-02 | International Business Machines Corporation | Dual mode phone line interface |
| US4856069A (en) * | 1987-04-16 | 1989-08-08 | Sudbury Systems, Inc. | Remote typing system |
| US5115233A (en) * | 1988-03-31 | 1992-05-19 | Motorola, Inc. | Shared data/voice communication system with programmable data priority |
| US4995055A (en) * | 1988-06-16 | 1991-02-19 | Hughes Aircraft Company | Time shared very small aperture satellite terminals |
| US5020076A (en) * | 1990-05-21 | 1991-05-28 | Motorola, Inc. | Hybrid modulation apparatus |
| JP3118819B2 (en) * | 1990-08-24 | 2000-12-18 | ソニー株式会社 | Remote control system |
| US5392460A (en) * | 1993-04-23 | 1995-02-21 | Nokia Mobile Phones Ltd. | Dual mode radiotelephone terminal selectively operable for frequency modulated or phase modulated operation |
| US5506572A (en) * | 1993-06-23 | 1996-04-09 | Lodgenet Entertainment Corporation | Low battery detection system |
| CA2154825A1 (en) * | 1994-09-09 | 1996-03-10 | Lars H. Mucke | Dual mode radiotelephone modulator |
| KR100976404B1 (en) * | 2007-10-30 | 2010-08-17 | 실리콤텍(주) | Control method and circuit for receiving signals in infrared receiver for remote control and infrared receiver having the control circuit |
| TWI500276B (en) * | 2010-03-22 | 2015-09-11 | Unwired Technology Llc | Dual-mode encoder, system including same, and method for generating infra-red signals |
| US9537324B2 (en) | 2011-12-14 | 2017-01-03 | Fleetwood Group, Inc. | Audience response system with batteryless response units |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL20201C (en) * | 1926-04-05 | |||
| US2514087A (en) * | 1947-04-18 | 1950-07-04 | Lawrence T Phelan | Modulated oscillator |
| US2881251A (en) * | 1953-12-31 | 1959-04-07 | Strip Joseph | Apparatus for time multiplexing speech and short bursts of information |
| US3761625A (en) * | 1972-03-15 | 1973-09-25 | Collins Radio Co | Digital method and means for frequency shift keying |
| DE2530812B2 (en) * | 1975-07-10 | 1977-08-18 | Loewe Opta Gmbh, 1000 Berlin | DIGITAL PULSE TRANSFER PROCESS FOR AN INFRARED REMOTE CONTROL |
| US4053717A (en) * | 1976-02-27 | 1977-10-11 | David Eugene Snider | Cordless telephone |
| DE2727335A1 (en) * | 1977-06-16 | 1978-12-21 | Bjoern Bluethgen | Data, text, or speech communications terminal - can carry out all possible communications functions over telephone lines, or by radio |
| US4160246A (en) * | 1977-10-03 | 1979-07-03 | Fairchild Camera And Instrument Corp. | Wireless multi-head smoke detector system |
| US4221932A (en) * | 1978-11-02 | 1980-09-09 | Bell Telephone Laboratories, Incorporated | Infrared remote signaling system |
-
1981
- 1981-04-06 US US06/251,258 patent/US4418416A/en not_active Expired - Lifetime
-
1982
- 1982-03-24 SE SE8201875A patent/SE452831B/en not_active IP Right Cessation
- 1982-04-02 FR FR8205746A patent/FR2503485B1/en not_active Expired
- 1982-04-03 DE DE19823212540 patent/DE3212540A1/en not_active Withdrawn
- 1982-04-05 BE BE0/207754A patent/BE892759A/en not_active IP Right Cessation
- 1982-04-05 IT IT20585/82A patent/IT1150532B/en active
- 1982-04-05 CA CA000400469A patent/CA1197559A/en not_active Expired
- 1982-04-05 NL NL8201448A patent/NL8201448A/en not_active Application Discontinuation
- 1982-04-05 GB GB8210049A patent/GB2097633B/en not_active Expired
- 1982-04-06 JP JP57057185A patent/JPS57193166A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE3212540A1 (en) | 1982-12-02 |
| IT8220585A1 (en) | 1983-10-05 |
| GB2097633B (en) | 1985-02-20 |
| FR2503485A1 (en) | 1982-10-08 |
| BE892759A (en) | 1982-08-02 |
| SE452831B (en) | 1987-12-14 |
| FR2503485B1 (en) | 1985-08-16 |
| NL8201448A (en) | 1982-11-01 |
| JPS57193166A (en) | 1982-11-27 |
| IT8220585A0 (en) | 1982-04-05 |
| IT1150532B (en) | 1986-12-10 |
| US4418416A (en) | 1983-11-29 |
| GB2097633A (en) | 1982-11-03 |
| SE8201875L (en) | 1982-10-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |