Frequency-burst-duration modulation and frequency multiplexed data transmission system

Claim 2

In a system for transmission of analog data over a single transmission channel from sensors at one of a plurality of remote stations to a central station, the cOmbination of means for transmitting an address signal from said central station to all of said remote stations to select a single one of said remote stations for acquiring analog data from sensors at said remote station, and initiate therein a data period, control means at an addressed station responsive to said address signal for initiating at the beginning of said data period transmission over said channel of a plurality of distinct tones associated with station sensors, one tone associated with each station sensor, and for simultaneously initiating a ramp signal, and means for terminating transmission of separate ones of said sensor tones when said ramp signal is equal to analog signals from associated sensors, whereby amplitude to tone duration conversion is accomplished for a plurality of analog sensors simultaneously.

Claim 3

The combination of claim 1 including means for terminating transmissions of all sensor tones not already terminated after said data period.

Claim 4

The combination of claim 2 including separate means at each remote station for transmitting at the end of said data period a station identifying tone over said channel thereby indicating to said central station that the addressed remote station has responded.

Claim 5

The combination of claim 3 wherein said control means at each station includes separate means for generating a distinct tone for each sensor, and separate switching means for simultaneously coupling each tone generating means to said common transmission channel at the beginning of said data period and symultaneously initiating said ramp signal.

Claim 6

The combination of claim 4 wherein said means for terminating transmission of separte ones of said sensor tones includes a separate means for comparing said ramp signal with a unique one of said analog sensor signals, and for producing a unique signal when said ramp signal is equal to the analog sensor signal being compared, and means responsive to each unique comparator signal for terminating transmission from an associated tone generating means over said transmission channel.

Claim 7

The combination of claim 5 wherein said station identifying means comprises means at each of said remote stations for generating a unique tone signal, and means for coupling said station identifying tone generating means to said transmission channel for a predetermined period at the end of said data period.

Claim 8

The combination of claim 6 including means at control central for receiving and separating said sensor tones transmitted over said channel into separate receiving channels, each receiving channel including means for demodulating the sensor tone therein to provide a received signal of a predetermined amplitude and a duration proportional to an original sensor signal, and means for integrating said received signal, thereby producing at an output terminal of said integrating means an analog output signal having an amplitude proportional to said original sensor signal.

Claim 9

In a system for transmission of analog data from sensors at remote stations to a control central station, each remote sensor station having a plurality of sensors, the combination of a transmission channel connecting said remote stations to said control central station, means for transmitting an address signal from said control central station to all of said remote sensor stations over said transmission channel to select a single one of said remote sensor stations for acquiring analog data from said sensor at said remote sensor station, control means at each remote sensor station responsive to said address signal for initiating transmission over said channel of a plurality of distinct tone associated with station sensors, one tone associated with each station sensor, and for simultaneously initiating a ramp signal, means for terminating transmission of separate tones associated with said sensors when said ramp signal is equal to analog signals from said associated sensors, whereby cOnversion of amplitude to frequency burst duration of a tone is accomplished for a plurality of analog sensors while simultaneously transmitting said plurality of said tones as frequency-division multiplexed signals, means at control central for receiving and demultiplexing said frequency-division multiplex signals into a plurality of duration modulated tone signals, means at control central for demodulating each of said duration modulated tone signals to provide a received signal proportional to an original sensor analog signal, and means at control central for temporarily storing said received signals.

Claim 10

In a system for transmission of analog data from sensors at remote stations to a control central station, each remote sensor station having a plurality of sensors, the combination of a transmission channel connecting said remote stations to said control central station, means for transmitting an address signal from said control central station to all of said remote sensor stations over said transmission channel to select a single one of said remote sensor stations for acquiring analog data from said sensor at said remote sensor station, control means at each remote sensor station responsive to said address signal for initiating transmission over said channel of a plurality of distinct tone associated with station sensors, one tone associated with each station sensor, and for simultaneously initiating a ramp signal, means for terminating transmission of separate tones associated with said sensors when said ramp signal is equal to analog signals from said associated sensors, whereby cOnversion of amplitude to frequency burst duration of a tone is accomplished for a plurality of analog sensors while simultaneously transmitting said plurality of said tones as frequency-division multiplexed signals, means at control central for receiving and demultiplexing said frequency-division multiplex signals into a plurality of duration modulated tone signals, means at control central for demodulating each of said duration modulated tone signals to provide a received signal proportional to an original sensor analog signal, and means at control central for temporarily storing said received signals.

Claim 11

The combination of claim 8 including separate means at each remote sensor station for transmitting over said channel a station identifying signal for a predetermined period after transmission from all sensor tone generating means has been terminated, thereby indicating to the control central that the addressed remote sensor station has responded.

Claim 12

The combination of claim 8 wherein said control means at each remote sensor station includes station identification means responsive to said address signal from said central station for producing a station activating pulse, separate means for generating a distinct tone for each sensor, and, separate switching means for simultaneously coupling each tone generating means to said common transmission channel and initiating said ramp signal in response to said remote sensor station activating pulse.

Claim 13

The combination of claim 10 wherein said means for terminating transmission of separate ones of said sensor tones includes a separate comparator means for comparing said ramp signal with each analog sensor signal, and for producing a unique signal when said ramp signal is equal to said analog signal, means for coupling said unique signal from each of said separate comparator means to distinct ones of said switching means, a unique signal from a given comparator means of an analog signal from one of said sensors being coupled to a switching means for an associated tone, and separate means within each switching means responsive to a unique signal coupled from a comparator means for decoupling an associated tone generating means from said common transmission channel, thereby producing frequency-burst-duration modulated and frequency-division multiplexed signals.

Claim 14

The combination of claim 11 including separate means for generating a station identifying tone at each remote sensor station, and means for coupling said station identifying tone generating means to said common transmission channel for a predetermined period after all sensor tone generating means have been decoupled from said transmission channel, thereby indicating to the control central that the addressed remote station has responded.

Claim 15

The combination of claim 8 wherein said demultiplexing means is comprised of separate means for band pass filtering each of the specific frequencies of tones of a given remote sensor station transmitted over said channel, and said demodulating means for a given filtered tone, which has been duration modulated by an analog sensor signal, is comprised of means for rectifying said given tone signal, a capacitor for filtering the output of said rectifying means, amplifying means for producing an output signal of predetermined amplitude when a minimum charge is stored in said capacitor, means for rapidly discharging filter capacitor to below said minimum to terminate said output signal when said given tone signal terminates, and means for integrating said output signal, thereby producing at an output terminal of said integrating means an analog output signal having an amplitude proportional to the duration of said given tone signal.

Claim 16

The combination of claim 13 including a memory capacitor, switching means for connecting said output terminal of said integrating means to said memory capacitor, thereby charging said memory capaCitor to the level of said analog output signal, in response to said output signal from said amplifying means.

Claim 17

The combination of claim 13 wherein said means for discharging said filter capacitor includes a field-effect transistor having a source, a drain and a gate connected with its source-drain circuit in parallel with said capacitor, said source being connected to one side of said capacitor, and said gate and drain being connected to the other side of said capacitor, where said one side is selected of a polarity which provides a high source-to-gate voltage to bias source-drain circuit current off when said capacitor is charged.

Claim 18

The combination of claim 15 wherein said drain is connected to said capacitor by a resistor.

Claim 19

The combination of claim 16 wherein said field-effect transistor is of the junction type and said gate is connected to said capacitor by a resistor.