Circuit arrangement for clock pulse recovery at the receiving end of digital clock-controlled data transmission systems

Claim 1

A circuit arrangement for clock pulse recovery in a digital, clock-controlled full duplex data transmission system in which analog information is converted into and transmitted in digital form and then reconverted into analog form, comprising: first and second transmitting/receiving stations and a transmission medium interconnecting said stations, said first transmitting/receiving station comprising a first transmitter and a first receiver and said second transmitting/receiving station comprising a second transmitter and a second receiver, said transmission medium comprising a first branch interconnecting said first transmitter and said second receiver and a second branch interconnecting said second transmitter and said first receiver; each of said transmitting/receiving stations further comprising a quartz-stabilized oscillator operable to produce pulses at a multiple of a desired clock pulse frequency; each of said transmitters comprising an analog/digital converter including an output connected to the respective transmission medium branch for outgoing transmission, a first input for receiving analog signals for conversion and a second input, and a first counter connected between the respective oscillator and said second input and operable in response to the oscillator pulses to feed clock pulses of the desired clock frequency to said analog/digital converter; each of said receivers comprising a digital/analog converter including a first input for connection to the respective transmission medium branch for incoming transmission, a second input for receiving recovered clock pulses, and an output for delivering analog signals, an EXCLUSIVE-OR gate including first and second inputs and an output, said first input connected in common with said first input of said digital/analog converter to said transmission medium branch for incoming transmission, a delay circuit connected across said first and second inputs of said EXCLUSIVE-OR gate, a second counter including a first input connected to the respective oscillator, an output connected to said second input of said digital/analog converter and a second input connected to the output of said EXCLUSIVE-OR gate, said second counter being reset upon opening of said EXCLUSIVE-OR gate and operable to recover and feed clock pulses to said digital/analog converter.