Abstract: To extend the transmission distance for basic rate integrated services digital network (ISDN) communications between a first site and a second site, the basic rate ISDN channel is demultiplexed onto a pair of half-rate digital subscriber loop channels, which employ an out of band maintenance channel to convey differential delay compensation information, but without modifying the framing structure of the transported channels, or requiring additional bandwidth for a separate framing channel. Halving the data rate, to increase the distance over which the basic rate ISDN channel may be transported, operates as a trade-off against loop loss, while still complying with ANSI standards.

Abstract: A method and system for interfacing a transmission facility with a digital subscriber line to enable transmission of digital voice communication and associated digital signalling are provided. A digital signal from the digital subscriber line is demultiplexed into a digital communication signal and a digital input control signal having a first sequence providing standard framing pattern, a second sequence providing signalling identification, and a third sequence providing signalling information. A monitor monitors the sequence of the input control signal and produces a signalling identification detect signal when the second sequence is detected and signalling enablement output when the third sequence is detected. The communication signal from the digital subscriber line is selectively multiplexed with the signalling information from the input control signal. The signalling information is output to the transmission facility when the signalling-enablement output is produced by the monitor.

Abstract: An analog data station terminal is described for use in a high speed data telecommunication system. The analog data station terminal interfaces a customer modem to the local telephone line for transmission of data at very high data rates, e.g., more than 9600 bits per second, with significant reduction in error rate. The analog data station terminal receives analog signals from the customer modem and converts then to a digital form that is compatible with the telephone system. The analog data station terminal also receives digital data from the telephone system and converts it to analog form for input to the customer modem. The formatting and reformatting of the data signals are performed synchronously with the telephone digital data network.

Abstract: A high-speed modem which acquires receiver operating parameters and equalizer coefficients, stores the parameters and coefficients after an initial modem communication having an initial training sequence, and reinitializes the modem equalizer and receiver at the beginning of subsequent modem transmissions with the previously stored coefficients and parameters to be followed by a shortened training sequence. The modem according to the present invention acquires the above-mentioned parameters and coefficients with improved accuracy by extending the initial training period before the transmission of data. The particular stored receiver parameters include carrier frequency offset and data timing frequency offset parameters. According to the present invention, an additional .DELTA. parameter is determined and stored which optimizes the receiver timing according to a difference between parameters acquired at different portions of the initial training sequence.