In a two-wire, full duplex data transmission system a circuit arrangement is described for carrying out an automatic adjustment of the value of the current flowing from the transmitter in a given station to a receiver therein relative to the value of the current supplied to that receiver from another station over a transmission line. A balancing circuit receives the station transmitter current and divides it into a plurality of sub-currents which are subsequently recombined and conducted to the ...

A device for the transmission of push-pull signals by way of a two-wire line in full duplex operation has a push-pull transmitter for the transmission of the push-pull signals to an opposite station and a push-pull receiver for the simultaneous reception of the push-pull signals transmitted from the opposite station, and a compensation circuit for compensating the push-pull signals transmitted from the associated push-pull transmitter in relation to the inputs of the push-pull receiver. The push...

A frequency modulation oscillator circuit is provided having three or more output frequencies corresponding to three or more possible input signals, the output frequency being a phase continuous frequency modulated signal with no discontinuities. For each desired output frequency, there is an input amplifier, responsive to an input binary signal, the output of that amplifier being summed with the outputs of the other amplifiers. For each input amplifier there is an active feedback network contai...

An improved quadraphase shift keyed (QPSK) adaptive demodulator includes a Costas loop modified to independently cross couple the inphase (I) and quadraphase (.phi.) channels so that minimum cross talk takes place between the I and Q channels. Advantageously, the improved QPSK adaptive demodulator separates the feedback control for correcting the phasor errors in the I and Q phasors. Advantageously, the improved demodulator permits independent phase adjustment of the I and Q demodulator outputs.

A phase synchronizing circuit for use in a multi-level, multi-phase, superposition-modulating signal transmission system is disclosed. The circuit includes a voltage-controlled oscillator which is responsive to a phase error signal. The output of the voltage-controlled oscillator is supplied as the reference input to a phase-detecting circuit. First and second demodulator circuits receive the output of the phase-detecting circuit and detect the superposition modulated signal. A logic circuit pro...

An error detection and correction system in which at least the highest order bit of each data word is given a greater protection against errors in transmission than lower order bits. Useful for digitized TV signals where errors in received high order bits have much worse effect on picture quality than errors in low order bits. A parity is generated for each data word in accordance with a self-orthogonal convolutional code constructed by the use of the base elements of a difference triangle for e...

A modulator for differentially encoded phase-shift keyed digital data is implemented entirely by digital means. Baseband serial binary data are illustratively transformed into dibit pairs which are assigned discrete quaternary carrier-wave phase shifts. A "staircasing" shift register whose weighted outputs are combined to form a quantized phase-modulated carrier wave is advanced by a relatively high-speed counter through a frequency divider network. The division rate of the divider is selectivel...

A frequency modulation oscillator is provided having three or more output frequencies corresponding to three or more possible input signals, the output frequency being a phase continuous frequency modulated signal with no discontinuities. For each desired output frequency, there is an input amplifier, responsive to an input binary signal, the output of that amplifier being summed with the outputs of the other amplifiers. For each input amplifier there is an active feedback network containing a d...

A message transmission system for the secure transmission of multi-block data messages from a sending station to a receiving station. The sending station contains cryptographic apparatus operative in successive cycles of operation during each of which an input block of clear data bits is ciphered under control of an input set of cipher key bits to generate an output block of ciphered data bits for transmission to the receiving station. Included in the cryptographic apparatus of the sending stati...

1. A receiver for use in a PSK signal translation system comprising a voltage tunable local oscillator for continuously generating a reference frequency signal from which the suppressed carrier can be reconstructed, input signal means for an incoming PSK signal, means for adding said reference frequency signal to produce a synthesized carrier which is amplitude modulated by said incoming PSK signal, diode switch means for demodulating synthesized PSK amplitude modulated carrier for causing synch...