Tie/communications, Inc.

Chestel, Inc.

Chansak Laoteppitaks

Alan Bloch

David L Joslow

Charles B Falconer

Lincoln Henthorn

A communication switching system of PABX uses a number of time division multiplexed send and receive highway pairs each servicing a plurality of peripheral devices or ports providing two-way communication with the outside world by means of associated telephones, trunk line interfaces, or similar apparatus. All highway pairs are multiplexed in accordance with the same time division format and the maximum number of two-way peripheral devices serviced by each highway pair is dependent on the number of time slots of the format assigned for audio communication. Each peripheral device transmits on a given audio time slot of its send highway. Switching to establish communication paths between peripheral devices is achieved in part by receiving means in each peripheral device responsive to command signals transmitted on command time slots on the associated receive highway instructing each peripheral device on which audio time slots of its receive highway to receive. A further part of the switching is provided by a plurality of highway switches in the common equipment which, under processor control, may forward the signal appearing in any given audio time slot of a send highway to the corresponding audio time slot of any selected one or more of the receive highways, thereby allowing each peripheral device to transmit an audio message to any other peripheral device of the system. Slot shifters are provided and used in cases where a peripheral device attempts to transmit to an audio time slot of a receive highway already in use. A central processor which communicates directly only with equipment in the common control formulates the command messages sent to the peripheral devices over the receive highways, formulates instructions controlling operation of the highway switches and otherwise supervises the functioning of the system. The arrangement of the system is one whereby it may be readily made up of whatever minimum number of highways pairs is necessary to yield the number of peripheral devices or ports necessary to suit the requirements of the office, plant or other facilities in which the system is to be installed, and whereby the capacity of the system, after installation, may be easily incrementally increased by adding additional highway pairs.

Muliple highway time division multiplexed PABX communication system

A decoder is disclosed for use in a communication system wherein bits of information are conveyed by the transmission, on a communication line, of code tones of distinctive frequencies each corresponding to a respective bit of information. The decoder divides an incoming signal into repetitive intervals having durations dependent on the period of the signal and provides digital measurements of the length of the interval by counting clock pulses during each interval. The digital measurements are then processed to test for persistence of the signal at a stable frequency for a predetermined time and for matching of said stabilized frequency to a recognized code tone frequency. More specifically, such decoder is disclosed as part of a larger decoder for use in, for example, a telephone communication system wherein dial numbers or other characters are communicated by way of simultaneously transmitted code tone pairs.

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Orange, CT, United States of America

Chansak Laoteppitaks