Signal multiplexing circuit

Details Signal multiplexing circuit Signal multiplexing circuit

H - Electricity

04

J

363/3

H04J 1/02 (2006.01) H04L 12/413 (2006.01) H04M 9/00 (2006.01) H04M 11/06 (2006.01)

Patent

CA 1230949

ABSTRACT OF THE DISCLOSURE Bidirectional communication of voice analog and data message signals over a two wire telephone line that interconnects several electronic key telephone station sets with a digital ac- cess circuit of a central data and voice communication facility is achieved by a multiplexing circuit that functions either as a set interface for a telephone or as a line card interface for the access circuit. Data messages originating at a key pad of any set or which are input to an interface bus of the multi- plexing circuit are stored in a shift register for subsequent modulation of a high band carrier signal, but only one interface may enter a transmission mode at one time. Transmission priority is therefore assigned by a controller to the interface that first attempts transmission on an inactive line, i.e., in the absence of the carrier signal. With transmission initiated, all other interfaces enter a monitor mode to listen but not act on the transmitted message. Errors in transmissions caused by line noise, or collision transmissions between two or more interfaces are resolved via message transactions between the interfaces. Retransmission priority based on the unique addresses of the calling interfaces resolves collision issues with priority going to the lowest address. Controllable transmit and receive equalizers define analog signal paths in the line card interface and are always in an operational mode. Corresponding equalizers in the set interface are normally quiescent and become fully operational only after a correct address match between calling and called interfaces occurs and the called interface responds with a line signal acknowledging receipt of a valid message. codec may then be enabled and bidirectional communication between a set and the facility is established with voice and signalling being frequency division multiplexed on the line.

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