At&t Bell Laboratories

Bell Telephone Laboratories

Radish Communications Systems, Inc.

Ronald K Witmore

Richard A Davis

Anthony J Brittain

Jerome J Zelenski

Charles J Fette

Peter Mathys

Thomas G Maxfield

A telecommunication system provides voice and data communications over a conventional telephone line that can be dynamically switched from voice mode to data mode during a single conversation. Each station includes a telephone for voice communications and bypass relay means for selectively connecting the telephone to the telephone line in voice mode and disconnecting the telephone while operating in data mode. Prior to transmitting data, the originating station first transmits a start signal over the telephone line that includes a rate signal indicating one of the several possible data transmission rates. If a station detects a start signal transmitted by a remote station, a microcontroller directs the bypass relay means and modem to automatically switch from voice mode to data mode in preparation for receiving data from the originating station.

Telecommunication display system

A time division, digital switching system capable of performing on-line testing of the actual communications paths that are switched is disclosed. When an idle network time slot is found, a test vector register places a stimulus in the idle time slot and the stimulus is directed to the address of an idle port. A loop-around path which includes a signature analysis chip (SAC) device is activated to divert a portion of the stimulus toward the SAC device. The response of the SAC device is gated to a maintenance circuit which reads the generated signature. Advantageously, the stimulus is selected to generate minimum noise at the addressed port so that if the user at the idle port picks up the telephone during the time slot used for testing, no loud noise will be heard.

Maintenance of stored program controlled switching systems

A programmed controlled signal processor operating as a time slot interchanger and having improved conferencing facilities is disclosed. A conference accumulator RAM is used that has a memory location unique to each conference call served by the system. A unique RAM location is assigned to the serving of each conference call in order to facilitate the generation of the required sum and difference signals. The use of an individual accumulator RAM position for this purpose permits the use of a simpler instruction set for the signal processor. This simpler instruction set permits a plurality of instructions for the serving of a given conference call to be interspersed with instructions for other calls rather than be contiguous to one another.

Time slot interchanger

A semiautonomous digit collection and call state detection subsystem is provided for use in a time division switching system such as a PBX. Each active (call serving) system port circuit applies a hook state signal to a specially provided bus during each occurrence of the time slot to which the port circuit is assigned. The subsystem's logic analyzes these hook state signals to identify certain predetermined call states and to count dial pulses. Output messages representing identified call states and dialed digits are made available to the switching system under control of a system scanner.

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Lafayette, CO, United States of America

Ronald K Witmore