Nortel Networks Corporation

Northern Telecom Limited

Michael J Lucas

Robert Barrie Turnbull

David Jeffrey Westergaard

Alan D Eyre

Brian Clifford McKinney

Bruce W Yee

A multi-line key telephone system not having a key service unit includes three analog telephone lines to which up to eight, three-line telephones may be connected to provide enhanced service features with cost-effectiveness. System reliability is maintained, notwithstanding a power dependency of the telephones, by including POTS telephones to provide uninterrupted essential telephone service in the event of a power outage. Both data and voice communications between two or more of the three-line telephones is achieved by converting an input digital bit stream from either a digital or analog source into a corresponding out-of-band binary FSK radio frequency output signal that is transceivingly communicated between the three-line telephones as data packets within a TDM frame. The out-of-band signal thus permits analog voice communications on the same line to proceed without interference. A telephone initiating a communications session acts as a master station, establishing inter-station communications synchronous at the frame level and asynchronous at the packet level. The called telephone functions as a slave station in a second time slot synchronized to a first time slot in the TDM frame received from the master. Temporary storage of data in firmware buffers and controlled timing at both the master and slave permits these stations to function within their respective TDM frame time slots.

Key telephone system without common control

A multi-line key telephone system not having a key service unit includes three analog telephone lines to which up to eight, three-line telephones may be connected to provide enhanced service features with cost-effectiveness. System reliability is maintained, notwithstanding the power dependency of the telephones, by including POTS telephones to provide uninterrupted essential telephone service in the event of a power outage. Both data and voice communications between two or more of the three-line telephones is achieved by converting an input digital bit stream from either a digital or analog source into a corresponding out-of-band binary FSK radio frequency output signal that is transceivingly communicated between the three-line telephones as data packets within a TDM frame. The out-of-band signal thus permits analog voice communications on the same line to proceed without interference. A telephone initiating a communications session acts as a master station, establishing inter-station communications synchronous at the frame level and asynchronous at the packet level. The called telephone functions as a slave station in a second time slot synchronized to a first time slot in the TDM frame received from the master. Temporary storage of data in firmware buffers and controlled timing at both the master and slave permits these stations to function within their respective TDM frame time slots.

A multi-line key telephone system not having a key service unit includes three analog telephone lines to which multiple telephone stations may be connected for enhanced communications between stations. Each station is connected by a modem to a single telephone line and includes a Universal Asynchronous Receiver Transmitter (UART) communicating with the modem, a microprocessor and a digital signal processor for effecting voice and data transfers and communicating time division multiplex protocol control to another telephone station on the same line. The UART includes a synchronizer with a master clock for defining positions of voice and data packets within a TDM frame having a predetermined data bit structure, and a receiver for acquiring a first valid packet header and start bit and issuing a sync pulse to adjust the master clock to conform to the timing of a new communication session. A receive data register in the UART temporarily stores data packets indexed to a first position within a TDM frame, and a receive voice buffer accumulates and temporarily stores voice packets indexed to a second position within the TDM frame. Transmitted data and voice packets are initially accumulated and stored as data and voice bytes in respective transmit data and voice registers of the UART from which the bytes are coupled to a transmitter for packetizing and subsequent transmission to the telephone line via the modem under control of the synchronizer.

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Airdrie, Canada

Michael J Lucas