Digital loop transceiver for interfacing a digital PABX to a digital subscriber set via a subscriber line
Patent 4432089 Issued on February 14, 1984. Estimated Expiration Date: 
December 24, 2001. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
December 24, 2001. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3924077 Digital private automatic branch exchange Circuit arrangement for the transmission of digital signals between subscriber stations of a time multiplex telecommunications network Circuit arrangement for telecommunications especially telephone installations that switch through digitally by time division Patent #: 4281410 InventorsAssigneeApplicationNo. 06/334412 filed on 12/24/1981US Classes:370/294, Time division370/376, Time slot interchange, per se370/377, Having supervisory signaling370/438, Using a separate control line or bus for access control370/458, Using time slots370/463, Details of circuit or interface for connecting user to the network370/522, Signaling (ancillary to main information)379/339With signal conversion (e.g., dial to DTMF, analog to PCM)ExaminersPrimary: Brigance, Gerald L.Attorney, Agent or FirmInternational ClassH04Q 11/04 (20060101)AbstractIn a digital telephone system, a digital private automatic branch exchange (PABX) has a plurality of digital line cards for coupling the PABX to respective digital subscriber sets via subscriber lines. In each digital line card, a digital loop transceiver operates in a master mode to couple the digital data bus of the PABX to the subscriber line via a subscriber line interface circuit in response to control signals provided by the PABX on the control bus thereof. In each digital subscriber set, a digital loop transceiver operates in a slave mode to couple the subscriber set to the subscriber line via a subscriber line interface circuit and to provide the several control signals required by the other components thereof. The digital loop transceivers provide communication on each of two communication channels, with the digital data words of the first channel being treated the same as the digital data words of the second channel.Other References
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