Communication circuit

Details Communication circuit Communication circuit

H - Electricity

04

M

379/33

H04M 19/00 (2006.01) H04B 3/44 (2006.01) H04L 5/20 (2006.01) H04M 9/00 (2006.01) H04Q 5/04 (2006.01)

Patent

CA 1112382

COMMUNICATION CIRCUIT A B S T R A C T The disclosure relates to a four conductor circuit arrangement providing two communication channels between a con- trol unit and a terminal device. Power feed and bi-directional signalling are accomplished simultaneously over the same four conductors used for the two communication channels without inter- ference. The signalling from the control unit to the terminal is accomplished by means of a voltage modulator circuit in the control unit by which voltage pulses are transmitted via a phan- tom circuit arrangement over the four conductors to the terminal unit. The voltage pulses are sensed from the phantom circuit in a data receiver which is located at the terminal unit. Connected to the phantom circuit in the terminal unit is a voltage regula- tor circuit which receives power from the control unit via the four conductor phantom circuit interconnecting the control unit and the terminal. In series with the voltage regulator circuit is a constant current sink and an inductor. A current modulator circuit is provided in parallel for impressing current data pul- ses generated in the terminal onto the phantom circuit, which are, in turn, received by a receiver circuit in the control unit. A preferred data format is disclosed as a method for transmitting information between the control units and the termi- nal. The preferred embodiment for the disclosed four con- ductor communication circuit and he disclosed data format is in a key telephone system in which the control unit is a station card in a key service unit and the terminal is a key telephone station set. - i -

304660

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