International Standard Electric Corporation

Donald Adams Weir

Eric Stanley Usher

Henley F Sterling

Anthony W Sweet

George A Howells

Rodger G George

William Arthur Walsh

John V Baxter

A line current detector for use in telecommunications systems to monitor line condition. The detector uses an optical or photo electric device whose input is modulated by line current. A photo transistor, electrically isolated from the line, senses the modulated output of the detector to produce a condition responsive output. The optical device is preferably a liquid crystal device. The output sensor is isolated from the line.

Line current detector

Telephone subscriber line circuits and an all-electronic telephone exchange are described wherein Hall effect devices are incorporated to detect line looping, dialing and ring-trip.

Subscriber line circuit

Data transmission in, for instance, a PCM system, is effected by translation of the binary codes into ternary combinations such that to each binary code there is provided n ternary codes with the choice of the ternary code sent being dependent on secondary intelligence, such as signalling information and/or synchronization information, to be sent. In the example described a binary bit stream is split into three bit blocks each of which is converted into a three bit ternary code.

Data transmission system for transmitting primary and secondary

Intelligence is conveyed in a PCM bit stream form with alternate bits being inverted. Additional information is conveyed by violations of the alternate bit rule so that two successive bits have the same polarity. Prior to being coupled to the alternate mark inversion coder a pseudo-random bit stream is mixed by binary addition without carry to the intelligence bit stream to maintain low DC level in the transmitted mixed bit stream and to maintain bit transitions relatively high.

Data transmission systems

Apparatus within a time division multiplex telecommunications system for terminating local traffic at a local distributing center and eliminating the need for use of channels to the switching center. The system employs time slots for calls to the switching center and other time slots for local calls. Digits representing the called line are stored in a register at the calling station. The register is interrogated after sufficient digits have been stored to inidicate the destination as local or switching center. When a local call is recognized, a bistable in the local distributing center is set. When the end of dialing signal is received, a code is generated to release the channel connection to the main exchange and to complete the call locally over time slots dedicated to serving local calls.

Local call completion for time division multiplexing system

An automatic telecommunication switching system is disclosed for switching TDM speech signals and data signals between calling and called parties. The system includes auxiliary circuits. Such circuits may include a monitor or comparator to detect the presence of a particular code. They may include a code converter for receiving a code of one variety and transmitting one of another variety or for changing the speed between reception and transmission.

Growing community of inventors

Goff's Oak, United Kingdom

Donald Adams Weir