Regenerative pcm line repeater

Claim 1

A two-way transmission line repeater for a pulse code modulation (PCM) transmission line system comprising for each direction of communication: a repeater input to receive distorted bipolar type PCM signals from said transmission line; a repeater output to transmit regenerated bipolar type PCM signals to said transmission line; an automatic equalizer circuit including a preamplifier having its input connected to said repeater input, a non-inverting output and an inverting output, a peak rectifier connected to both said non-inverting and said inverting outputs of said preamplifier, a reference voltage source, a variable line compensating network havIng a control input and an output coupled to the input of said preamplifier, and an amplitude comparator coupled to said reference voltage source and the output of said peak rectifier to produce a control signal for coupling to said control input to maintain a constant amplitude signal at both said non-inverting and said inverting outputs of said preamplifier; a clock extraction circuit including an averaging rectifier coupled to said non-inverting and said inverting outputs of said preamplifier, a tank circuit tuned to the bit rate of said distorted PCM signals coupled to the output of said averaging rectifier, said tank circuit producing sine waves having a frequency equal to said bit rate and zero crossings shifted 90* with respect to the peaks of said distorted PCM signals, a 90* phase shifter and amplitude limiter coupled to said tank circuit to produce first square wave timing pulses having a frequency equal to said bit rate, a 50 percent duty cycle and negative going transitions coincident with the peaks of said distorted PCM signals, and a differentiator and inverter coupled to said phase shifter and limiter to differentiate the negative going transitions of said first timing pulses and to invert the differentiated negative going transitions to produce second timing pulses; and a pulse regenerator including a threshold voltage source to provide a given threshold voltage, a first threshold circuit coupled to said threshold voltage source and said non-inverting output of said preamplifier to produce a binary ''''1'''' when said distorted PCM signals on said non-inverting output exceeds said threshold voltage, a second threshold circuit coupled to said threshold voltage source and said inverting output of said preamplifier to produce a binary ''''1'''' when said distorted PCM signals on said inverting output exceeds said threshold voltage, a first AND gate coupled to the output of said first threshold circuit and said differentiator and inverter responsive to said second timing pulses, a second AND gate coupled to the output of said second threshold circuit and said differentiator and inverter responsive to said second timing pulses, a first bistable device having its ''''1'''' input coupled to the output of said first AND gate and its ''''0'''' input coupled to said phase shifter and limiter responsive to the positive going transitions of said first timing pulses to regenerate the positive pulses of said distorted bipolar PCM signals, a second bistable device having its ''''1'''' input coupled to the output of said second AND gate and its ''''0'''' input coupled to said phase shifter and limiter responsive to the positive going transitions of said first timing pulses to regenerate the negative pulses of said distorted bipolar PCM signals, and means coupled between the ''''1'''' output of both said first and second bistable devices and said repeater output to combine the resultant output signals of said first and second bistable devices to provide said regenerated bipolar PCM signals.