International Business Machines Corporation

Paul Abramson

Lee C Haas

David E Conner

Ulrich Appel

The multiplexing circuit disclosed herein combines multiple input signals into a common output by allowing ternary signals to pass from multiple input circuits to a common output circuit. The circuit combines ternary signals with minimum feedback between input circuits. The circuit is passive, has minimum attenuation, and a small number of components.

Ternary signal multiplexor circuit

This invention details a baseband bipolar pulse signaling technique employing only two wires for simultaneous bi-directional communications. A first polarity of pulses is utilized for communication of traffic in one direction; traffic in the return direction utilizes pulses of the opposite polarity. Each end of the communication link has both a sender and a receiver. One sender arbitrarily transmits only positive pulses; the receiver at this end of the system will recognize only negative pulses. The inverse set of conditions is enforced at the opposite end of the link. Means are included for synchronizing the application of pulses to the link at the other end in response to the receipt of pulses at that end to avoid overlap of receive pulses at the originating end of the line.

Two wire bi-directional digital telephone link

A connection system for varied distance digital communication capable of handling telephone signals utilizes Voice Activity Compression (VAC) to effectively share a given number of digital transmission channels among a greater number of virtual telephone connections. The telephone signals are delta-modulated and demodulated in system connection stations. The VAC processing circuits with a small increment of decision logic provide echo suppression. Echo suppression is thereby rendered as a 'value-added' service at a relatively small increment of station cost over the cost of VAC processing. Echo interference with original telephone signal activity in the send channels is reduced by digital control of gain in the demodulation stage. The system also provides connections without VAC handling subject to echo control.

Growing community of inventors

Raleigh, NC, United States of America

Paul Abramson