Crystal controlled frequency shift keying synchronous generating system

Claim 2

A transmitter for generating frequency shift keying signals for application to a communications channel in response to digital information signals applied to said transmitter by an input device, said transmitter comprising: first crystal controlled generating means including input circuit means coupled to said input device and output circuit means, said first generating means being arranged to produce output pulse signals of predetermined repetition frequencies at said output circuit means for application to said channel in response to said digital information signals applied to said input circuit means; second generating means coupled to said input device and being arranged to produce output pulse signals whose repetition frequencies approximate said predetermined repetition frequencies; and, frequency selection and control means coupled to said first and second generating means and being operative in response to a change in state of said digital information signals signifying a shift in frequency to condition said first generator means so as to substitute selectively pulse signals produced by said second generating means.

Claim 3

The transmitter according to claim 1 further including: control logic means coupled to receive said digital information signals from said input device, said control logic means including means for generating a plurality of bilevel selection signals in response to said digital information signals and means for applying said selection signals jointly to said input means of said first generating means, and to said second generating means, said first and second generating means being operative to produce said output pulse signals whose repetition frequencies are established in accordance with the states of said bilevel selection signals.

Claim 4

The transmitter of claim 1 further including means coupling said output circuit means of said first crystal controlled generating means to said second generating means for conditioning said second generating means to produce said output pulse signals in synchronism with said pulse signals produced by said first generating means.

Claim 5

The transmitter of claim 3 further including frequency divider means coupled to said output circuit means of said first crystal controlled generating means for receiving said output pulse signals, said divider means being operative to produce a square wave pulse whose repetition frequency is a submultiple of the repetition frequency of said output pulse signal; and, conversion means coupled to said divider means and to said channel, said conversion means being operative in response to said square wave pulses to produce a sine wave whose frequency corresponds to the frequency selected.

Claim 6

The transmitter of claim 4 wherein said frequency divider means includes bistable complementing means arranged to produce said square wave pulses whose repetition frequency is one-half of said repetition frequency of said output pulse signals.

Claim 7

The transmitter of claim 5 wherein said conversion means includes active low pass filter means coupled to said complementing means and being operative to extract said sine wave from said square wave pulses.

Claim 8

A frequency shift keying transmitter for generating at least two frequencies for application to a communications channel in response to bilevel selection signals applied to a plurality of input selection lines, said transmitter comprising: first generating means coupled to said selection lines and arranged to produce output pulse signals of predetermined repetition frequencies in response to said bilevel selection signals; second generating means having a plurality of input terminals and an output terminal, said input terminals being connected to said input selection lines and said second generating means being operative in response to each of said bilevel selection signals to produce an output pulse signal at said output terminal whose repetition frequencies approximate said predetermined repetition frequencIes; and, frequency selection and control means coupled to said first and second generator means and being operative in response to changes in state of said selection signals signifying a shift from a prior selected repetition frequency to a new selected repetition frequency to condition said first generator means so as to selectively substitute pulse signals from said second generating means for said pulse signals produced by said first generating means in accordance with said new selected repetition frequency in a manner so as to minimize crossover distortion of said frequencies of said output pulse signals during each change in state in said selection signals.

Claim 9

A frequency shift keying transmitter for generating at least two frequencies for application to a communications channel in response to bilevel selection signals applied to a plurality of input selection lines, said transmitter comprising: first generating means coupled to said selection lines and arranged to produce output pulse signals of predetermined repetition frequencies in response to said bilevel selection signals; second generating means having a plurality of input terminals and an output terminal, said input terminals being connected to said input selection lines and said second generating means being operative in response to each of said bilevel selection signals to produce an output pulse signal at said output terminal whose repetition frequencies approximate said predetermined repetition frequencIes; and, frequency selection and control means coupled to said first and second generator means and being operative in response to changes in state of said selection signals signifying a shift from a prior selected repetition frequency to a new selected repetition frequency to condition said first generator means so as to selectively substitute pulse signals from said second generating means for said pulse signals produced by said first generating means in accordance with said new selected repetition frequency in a manner so as to minimize crossover distortion of said frequencies of said output pulse signals during each change in state in said selection signals.

Claim 10

The transmitter of claim 7 wherein said first generating means is crystal controlled and said output terminal of said first generating means is coupled to said second generating means for conditioning said second generating means to produce pulse signals in synchronism with the output pulse signals produced by said first generating means.

Claim 11

The transmitter according to claim 8 wherein said first generating means includes; a crystal controlled oscillator means arranged to produce pulses of a single repetition frequency; binary counter means coupled to said oscillator means and being operative in response to said pulses to be incremented through successive counts; and, logic means having a plurality of input terminals and an output terminal, predetermined ones of said input terminals being coupled to a different one of said selection lines and other ones of said input terminals being coupled to said counter means in a manner so as to apply to said output terminal pulse signals of a predetermined repetition rate established by different counts of said counter means selected in accordance with said status of said selection signals; and, said logic means being coupled to said frequency selection and control means and being conditioned by said control means in response to said changes in the states of said selection signals to inhibit selectively the application to said output terminal of pulse signals derived from counts of said counter means and to pass pulse signals from said second generating means.

Claim 12

The transmitter according to claim 9 wherein said second generating means includes: ramp generating means having a plurality of input terminals and an output terminal, one of said input terminals being coupled to the output terminal of said logic means and each of the other of said input terminals being coupled to a different one of said selection lines, said ramp generating means being operative in response to each of said bilevel selection signals to produce a ramp voltage waveform of a predetermined repetition frequency; and, comparator amplifier switching means having an input terminal directly coupled to said output terminal of said ramp generating means and an output terminal coupled to said frequency selection and control means, said switching means being operative in response to a predetermined voltage level of said ramp waveform to produce a rectangular waveform of a frequency equal to the selected repetition frequency of said ramp voltage waveform.

Claim 13

The transmitter according to claim 10 wherein said ramp generating means includes: a transistor current source having an input circuit and an output circuit; a plurality of gating means, each of said gating means having an input terminal and an output terminal, said input terminal being coupled to a predetermined one of said input terminals; a plurality of resistor means, each of said resistor means being coupled to said input circuit in series with the output terminal of a different one of said gating means and each being arranged to apply a predetermined voltage level to said input circuit upon the activation of said gating means to condition said transistor current source to supply a predetermined amount of current; capacitor storage means coupled to said transistor output circuit for proDucing a linear ramp voltage waveform whose repetition frequency is determined by the selection of said gating and resistor means in accordance with the state of said bilevel selection signal; and, amplifier switching means coupled to said capacitor storage means and being operative to generate said first set of pulse signals at said output terminal in response to predetermined voltage levels of said voltage waveform.

Claim 14

The transmitter according to claim 11 wherein each of said gating means including a transistor inverter circuit having base, emitter, and collector electrodes, said base electrode being coupled to said input terminal for receiving said selection signal, said emitter electrode being coupled to ground potential and said collector electrode being coupled to said output terminal whereby said inverter circuit is operative in response to said selection signal to couple said resistor means associated therewith to said ground potential so as to apply said predetermined voltage level.

Claim 15

The transmitter according to claim 9 wherein said frequency selection and control means includes: an input section, said input section including a plurality of gating means coupled to said input selection lines and coupled to said counter means, each of said gating means being arranged to combine selectively signals from said counter means representative of said counts with a different one of said selection signals to produce said pulse signals of a predetermined repetition frequency; an output section coupled to said input section and to said output terminal for selectively applying said output pulse signals, said output section including pulse reset means coupled to said counter means and to said one input terminal of said ramp generating means, said pulse reset means being operative in response to each of said output pulse signals to force said counter means and said ramp generating means to an initial state; and, bistable control means coupled to said selection lines, said bistable control means being operative to produce a first control signal when switched to a first state in response to a change in state in any one of said selection signals and being operative to produce a second control signal when switched to a second state by said pulse reset means; said output section being conditioned by said second control signal to cause said reset means to produce a reset pulse in response to pulse signals from said comparator switching means for resetting said counter means to said initial state so as to have the repetition frequency of said output pulse signals established by the counts of said counter means as specified by said selection signals, said output section being operative in response to said first control signal to condition said pulse reset means to reset said counter means in response to said pulse signals from said second generating means so as to have the period of each of said output pulse signals during said changes of state established by said second generating means within the limits of said prior selected frequency and said new selected frequency as specified by said selection signals thereby minimizing said crossover distortion of said output pulse signals.

Claim 16

The transmitter according to claim 13 wherein each of said gating means of said input section includes: an AND gate having a plurality of input terminals and an output terminal, said input terminals connected to receive said different one of said input selection lines and selected output signals and said AND gate being operative to produce an output pulse signal whose frequency corresponds to the cycle time of said counter means in accordance with a predetermined count defined by said output signals; and, wherein said output section includes: a plurality of AND gates, each number of said AND gates having a pair of input terminals and an output terminal, one of said input terminals of a number of each of said gates being connected to a different one of said input section AND gate output terminals and the other one of said input terminals of each of said gates being coupled to said bistable control means to receive said first control signal and one input terminal of one of said plurality being connected to said output terminal of said ramp generating means and the other input terminal of said gate being coupled to said bistable control means to receive said second control signal, said output section, being operative to pass selectively output pulse signals through one of said plurality of AND gates from a selected one of said one of said plurality in accordance with the state of said first and second control signals.

Claim 17

The transmitter of claim 13 further including: frequency divider means coupled to said pulse reset means of said output section for receiving said output signal, said divider means being operative to produce an output square wave waveform which is a submultiple of the fundamental frequency of said output signal; and, conversion means coupled to said divider means and to said channel, said conversion means being operative in response to said square wave waveform to provide a sinusoidal waveform of the frequency selected.

Claim 18

The transmitter of claim 15 wherein said frequency divider means includes bistable complementing means arranged to produce said square wave pulses whose repetition frequency is one-half of said repetition frequency of said output pulse signals.

Claim 19

The transmitter of claim 15 wherein said pulse reset means includes: first pulse generating means having an input terminal and an output terminal, said input terminal being connected to the output terminals of each of said AND gates of said output section; said first pulse generating means being operative to produce a first pulse in response to the leading edge of a pulse from said counter means for switching said ramp generator means to said initial state for switching the state of said complementing means; and, second pulse generating means being operative at the termination of said first pulse to generate a second pulse for switching said bistable control means to said second state.

Claim 20

The transmitter of claim 17 wherein said first and second pulse generating means are one-shot circuits adapted to produce pulses whose widths are selected to be much smaller than the period of said ramp generating means.

Claim 21

A transmitter for producing frequency shift keying signals in response to an input binary information signal comprising: a stable pulse generator operative to produce pulse signals of a predetermined repetition frequency; a counter coupled to said generator and being arranged to count said generator pulse signals; selectively operable means coupled to said counter for resetting said counter to an initial state when said counter advances to different predetermined counts so as to provide output signals at the respective rates of said resetting of said counter; generating means for selectively generating pulse signals at variable rates corresponding to said frequencies of said output signals provided by said counter; an output terminal; first logic means coupled to said selectively operable means and being conditioned by said binary information signal normally to pass to said output terminal said output signals of said counter; and, second logic means being coupled to said operable means and being responsive to a change of state in said binary signal to condition said operable means to change the frequency of said output signals of said counter, said second logic means being further coupled to said first logic means and to said generating means for disabling said first logic means and for applying said output pulse signals of said generating means to said output terminal in response to said change of state in said binary signal.

Claim 22

A transmitter for producing frequency shift keying signals in response to an input binary information signal comprising: a stable pulse generator operative to produce pulse signals of a predetermined repetition frequency; a counter coupled to said generator and being arranged to count said generator pulse signals; selectively operable means coupled to said counter for resetting said counter to an initial state when said counter advances to different predetermined counts so as to provide output signals at the respective rates of said resetting of said counter; generating means for selectively generating pulse signals at variable rates corresponding to said frequencies of said output signals provided by said counter; an output terminal; first logic means coupled to said selectively operable means and being conditioned by said binary information signal normally to pass to said output terminal said output signals of said counter; and, second logic means being coupled to said operable means and being responsive to a change of state in said binary signal to condition said operable means to change the frequency of said output signals of said counter, said second logic means being further coupled to said first logic means and to said generating means for disabling said first logic means and for applying said output pulse signals of said generating means to said output terminal in response to said change of state in said binary signal.

Claim 23

A transmitter for generating at least two frequencies for application to a communications channel in response to biLevel selection signals applied to a plurality of input selection lines, said transmitter comprising: crystal controlled oscillator means arranged to produce an output signal of a single fundamental frequency; counter means including a plurality of series connected bistable means, a first one of said bistable means being coupled to said oscillator means for receiving said output signal, each bistable means being operative to produce an output signal whose frequency is a different submultiple of said single frequency; ramp generating means having a plurality of input terminals and an output terminal, said input terminals being connected to said input selection lines and said ramp generating means being operative in response to each of said bilevel signals to produce a first set of pulse signals at said output terminal of a different predetermined fundamental frequency; and, frequency selection and control means including: an input section, said input section including a plurality of gating means coupled to said input selection lines and coupled to said plurality of bistable means, each of said gating means being arranged to selectively combine output signals of predetermined ones of said series of bistable means with a different one of said selection signals to produce a second set of pulse signals of a predetermined fundamental frequency for application to an output terminal specified by said selection signals; an output section coupled to said input section and to said ramp output terminal for selectively applying as an output signal said first and second sets of pulse signals, said output section including pulse reset means coupled to said counter means, said pulse reset means being operative in response to said output signals to produce a reset signal to force said counter means to an initial state; and, bistable control means coupled to said input terminals and being operative to produce a first control signal when switched to a first state in response to a change in state in any one of said bilevel selection signals, said bistable means being coupled to said output means and being operative to produce a second control signal when switched to a second state by said pulse reset means; said output section being conditioned by said second control signal to condition said reset means to reset said counter means in response to said second set of pulse signals so as to have the repetition frequency of said output signal established only by the cycling rate of said counter means as specified in accordance with the state of said input selection signals and said second set of pulse signals, said output section being operative in response to said first control signal to condition said pulse reset means to reset said counter means in response to said first set of pulse signals to have the period of said output signal within limits established by said fundamental frequencies of said ramp generating means selected in accordance with said change of state in said bilevel selection signals thereby providing an output signal of nominal duration during the crossover time when shifting between frequencies.

Claim 24

A transmitter for generating at least two frequencies for application to a communications channel in response to biLevel selection signals applied to a plurality of input selection lines, said transmitter comprising: crystal controlled oscillator means arranged to produce an output signal of a single fundamental frequency; counter means including a plurality of series connected bistable means, a first one of said bistable means being coupled to said oscillator means for receiving said output signal, each bistable means being operative to produce an output signal whose frequency is a different submultiple of said single frequency; ramp generating means having a plurality of input terminals and an output terminal, said input terminals being connected to said input selection lines and said ramp generating means being operative in response to each of said bilevel signals to produce a first set of pulse signals at said output terminal of a different predetermined fundamental frequency; and, frequency selection and control means including: an input section, said input section including a plurality of gating means coupled to said input selection lines and coupled to said plurality of bistable means, each of said gating means being arranged to selectively combine output signals of predetermined ones of said series of bistable means with a different one of said selection signals to produce a second set of pulse signals of a predetermined fundamental frequency for application to an output terminal specified by said selection signals; an output section coupled to said input section and to said ramp output terminal for selectively applying as an output signal said first and second sets of pulse signals, said output section including pulse reset means coupled to said counter means, said pulse reset means being operative in response to said output signals to produce a reset signal to force said counter means to an initial state; and, bistable control means coupled to said input terminals and being operative to produce a first control signal when switched to a first state in response to a change in state in any one of said bilevel selection signals, said bistable means being coupled to said output means and being operative to produce a second control signal when switched to a second state by said pulse reset means; said output section being conditioned by said second control signal to condition said reset means to reset said counter means in response to said second set of pulse signals so as to have the repetition frequency of said output signal established only by the cycling rate of said counter means as specified in accordance with the state of said input selection signals and said second set of pulse signals, said output section being operative in response to said first control signal to condition said pulse reset means to reset said counter means in response to said first set of pulse signals to have the period of said output signal within limits established by said fundamental frequencies of said ramp generating means selected in accordance with said change of state in said bilevel selection signals thereby providing an output signal of nominal duration during the crossover time when shifting between frequencies.

Claim 25

The transmitter of claim 20 wherein said ramp generating means is coupled to said pulse reset means and is adapted to be reset to an initial state by said reset means so as to produce said first set of pulse signals in synchronism with said second sets of pulse signals produced by said counter means.

Claim 26

The transmitter of claim 20 further including: frequency divider means coupled to said output section for receiving said output signal, said divider means being operative to produce an output square wave waveform which is a submultiple of the fundamental frequency of said output signal; and, conversion means coupled to said divider means and to said channel, said conversion means being operative in response to said square wave waveform to provide a sinusoidal waveform of the frequency selected.

Claim 27

The transmitter of claim 22 whereiN said conversion means includes active low pass filter means coupled to said complementing means and being operative to discriminate against all frequencies higher than the highest frequency to be transmitted by said transmitter.

Claim 28

The transmitter of claim 23 wherein said complementing means includes a D-type flip-flop connected to complement.

Claim 29

The transmitter according to claim 20 wherein each of said gating means of said input section includes: an AND gate having a plurality of input terminals and an output terminal, said input terminals connected to receive said different one of said input selection lines and selected output signals and said AND gate being operative to produce an output pulse signal whose frequency corresponds to the cycle time of said counter means in accordance with a predetermined count defined by said output signals; and wherein said output section includes: a plurality of AND gates, each of a number of said AND gates having a pair of input terminals and an output terminal, one of said input terminals of a number of each of said gates being connected to a different one of said input section AND gate output terminals and the other one of said input terminals of each of said gates being coupled to said bistable control means to receive said first control signal and one input terminal of one of said plurality being connected to said output terminal of said ramp generating means and the other input terminal of said gate being coupled to said bistable control means to receive said second control signal, said output section being operative to selectively pass output pulse signals through one of said plurality of AND gates from a selected one of said input AND gates and said one of said plurality in accordance with the state of said first and second control signals.

Claim 30

The transmitter according to claim 25 wherein said bistable control means includes: a flip-flop having a set input and a reset input; first pulse generating means having an input terminal and an output terminal, said input terminal being coupled to said input selection lines and said output terminal being coupled to said set input of said flip-flop; second pulse generating means having an input terminal and an output terminal, said input terminal being coupled to said input selection lines and said output terminal being coupled to said set input of said flip-flop; and, third pulse generating means having an input terminal and an output terminal, said input terminal being coupled to said pulse reset means and said output terminal being coupled to said reset input of said flip-flop, said first pulse generating means and second pulse generating means respectively being operative to produce an output pulse in response to positive and negative going transitions of said bilevel selection signals for switching said flip-flop to said first state and said third pulse generating means being operative to switch said flip-flop to said second state in response to said reset signal from said pulse reset means.

Claim 31

The transmitter of claim 26 wherein said pulse reset means includes: first pulse generating means having an input terminal and an output terminal, said input terminal being connected to the output terminals of each of said AND gates of said output section; said first pulse generating means being operative to produce a first pulse in response to the leading edge of a pulse from said counter means for switching said ramp generator means to said initial state and for switching the state of said complementing means; and, second pulse generating means being operative at the termination of said first pulse to generate a second pulse for switching said flip-flop to said second state.

Claim 32

The transmitter of claim 27 wherein said first and second pulse generating means are one-shot circuits adapted to produce pulses whose widths are selected to be much smaller than the period of the waveforms produced by said ramp generating means.

Claim 33

The transmitter of claim 20 wherein said ramp generating means includes: a transistor current source having an input circuit and an output circuit; a plurality of gating means, each of said gating means having an input terminal and an output terminal, said input terminal being coupled to a predetermined one of said input terminals; a plurality of resistor means, each being coupled to said input circuit in series with the output terminal of a different one of said gating means and each being arranged to apply a predetermined voltage level to said input circuit upon the activation of said gating means to condition said transistor current source to supply a predetermined amount of current; capacitor storage means coupled to said transistor output circuit for producing a linear ramp voltage waveform whose repetition frequency is determined by the selection of said gating and resistor means in accordance with the state of said bilevel selection signals; and, amplifier switching means coupled to said capacitor storage means and being operative to generate said first set of pulse signals at said output terminal in response to predeternined voltage levels of said voltage waveform.

Claim 34

The transmitter according to claim 29 wherein each of said gating means includes a transistor inverter circuit having base, emitter, and collector electrodes, said base electrode being coupled to said input terminal for receiving said selection signal, said emitter electrode being coupled to ground potential and said collector electrode being coupled to said output terminal whereby said inverter circuit is operative in response to said selection signal to couple said resistor means associated therewith to ground so as to apply said predetermined voltage level.

Claim 35

A data modem for transmitting FSK signals to a communication channel in response to binary information signals applied from an input device, said modem comprising: control logic means coupled to said input device and being operative in response to said binary information signals to generate at least first and second bilevel selection signals; first generating means including: crystal controlled oscillator means for generating pulses of a predetermined repetition rate; and, frequency divider means including a plurality of series coupled bistable means, a first of said bistable means being coupled to said oscillator means to receive said pulses; logic gating and control means having a plurality of input terminals being coupled to receive a different one of said selection signals and being coupled to predetermined ones of said bistable means for receiving pulse signals representative of different predetermined counts, said output terminal being coupled to said each of said bistable means of said divider means and said logic gating and control means being conditioned in accordance with said selection signals to pass pulse signals representative of one of said predetermined counts to said output terminal conditioning said divider means to produce subsequent pulse signals of said one of said predetermined counts corresponding to a predetermined repetition frequency; and, second generating means having a plurality of input terminals and an output terminal, each of said input terminals being coupled to receive a different one of said selection signals and said output terminal being coupled to said logic gating means, said second generating means being operative when conditioned by one of said selection signals to generate pulse signals at a predetermined repetition rate approximating the rate of the pulse signals produced by said selected count and said logic gating and said control means being conditioned by said selection signals during a shift from a prior frequency to a new frequency to selectively substitute pulse signals produced by said second generating means for said pulse signals produced by said count in a manner so as to establish durations for said pulse signals applied to said output terminal no shorter than the shorter of the two frequencies designated during each shift in frequency.

Claim 36

A data modem for transmitting FSK signals to a communication channel in response to binary information signals applied from an input device, said modem comprising: control logic means coupled to said input device and being operative in response to said binary information signals to generate at least first and second bilevel selection signals; first generating means including: crystal controlled oscillator means for generating pulses of a predetermined repetition rate; and, frequency divider means including a plurality of series coupled bistable means, a first of said bistable means being coupled to said oscillator means to receive said pulses; logic gating and control means having a plurality of input terminals being coupled to receive a different one of said selection signals and being coupled to predetermined ones of said bistable means for receiving pulse signals representative of different predetermined counts, said output terminal being coupled to said each of said bistable means of said divider means and said logic gating and control means being conditioned in accordance with said selection signals to pass pulse signals representative of one of said predetermined counts to said output terminal conditioning said divider means to produce subsequent pulse signals of said one of said predetermined counts corresponding to a predetermined repetition frequency; and, second generating means having a plurality of input terminals and an output terminal, each of said input terminals being coupled to receive a different one of said selection signals and said output terminal being coupled to said logic gating means, said second generating means being operative when conditioned by one of said selection signals to generate pulse signals at a predetermined repetition rate approximating the rate of the pulse signals produced by said selected count and said logic gating and said control means being conditioned by said selection signals during a shift from a prior frequency to a new frequency to selectively substitute pulse signals produced by said second generating means for said pulse signals produced by said count in a manner so as to establish durations for said pulse signals applied to said output terminal no shorter than the shorter of the two frequencies designated during each shift in frequency.