Electronic key telephone system

Details Electronic key telephone system Electronic key telephone system

H - Electricity

04

M

363/22, 379/33,

H04M 3/42 (2006.01) H04M 9/00 (2006.01) H04Q 3/545 (2006.01)

Patent

CA 1174773

ELECTRONIC KEY TELEPHONE SYSTEM Abstract of the Disclosure Each of the station sets in the system generates a continuous, current-modulated digital data stream carrying information concerning the status of pushbutton-actuated switches associated with a particular service or feature. This data stream is transmitted via a phantom pair over standard four-wire cable to an associated station card in the key service unit, which receives and decodes the data, implements any service requested at the associated station set by closure of a pushbutton-actuated switch in the station set, and generates a continuous voltage-modulated digital data stream carrying instructions for the connection of the station set speakerphone to either the first or second talk path formed by the first and second conductor pairs in the standard four-wire cable, for energization of light-emitting diodes associated with the pushbutton-actuated switches in the station set, and for controlling background music transmission to the associated station set. This data stream is transmitted via the aforementioned phantom pair to the station set, which receives and decodes the data and carries out the instructions contained therein. Each station card and each station set incorporates a stored-program digital microcomputer for de- coding the received data and for generating the data to be transmitted. Each station card also includes a series of cross- points in the form of field-effect transistors, the gate elec- trodes of which are connected to crosspoint latches controlled by the microcomputer. Each crosspoint has an associated input terminal in a status multiplexer which receives data from the passive port to which the associated crosspoint is connected. Each crosspoint and its associated status multiplexer input terminal constitute an active port. Each station card also includes at least one passive port for hotline connection to an active port of another station card or cards, and may also include a passive port for connection to the active ports of one or more link cards. Other system component circuits are dis- posed on line cards having a single passive port, an internal conference card having a single passive port, a page card having multiple passive ports, a register card or cards con- nected to the link card or cards, and a tone generator card.

335220

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