Showing papers on "High-bit-rate digital subscriber line published in 1974"

Subscriber digital multiplexing system with time division concentration

Abstract: A digital multiplexer for transmitting control, signaling and speech information in digital form between a central telecommunications office (CO) and a plurality of remote terminals. The system serves a plurality of lines at the exchange and couples those lines to subscriber stations associated with those lines through a digital span line such as the generally known Tl line between a CO terminal and the remote terminals. A maximum of 32 channels are provided using continuously variable slope delta modulation, with the modulation and demodulation being performed in line circuits individual to each line being served. A time division concentration stage enables the system to service 128 lines over the 32 channels with each channel having a memory position for storage of line address information.

Method of transmitting digital information in a time-division multiplex telecommunication network

Abstract: A method for transmitting digital data in a time-division multiplex telecommunications network over subscriber lines connecting digital subscriber stations to a subscriber concentrator is described. Transfers of data occur over two wire subscriber lines in both transmission directions in a time interleaved manner alternatively and in the form of bits. The bits are formed to have a duration such that in conjunction with the distance/velocity lags of transmission over subscriber lines they almost completely use the sampling intervals or pluralities thereof. This forms the basis for transmisson over time division multiplex paths going out from the subscriber concentrator and coming in thereat, except for a tolerance time interval allowed for the period of the clock generators determining the bit rate in the subscriber sets relative to the period of the exchange clock generator determining the exchange clock rate in the exchange connected to the subscriber concentrator.

Subscriber Line Equipment for an Elastic Carrier Switching System

Abstract: This is the third of three papers [l], [2] dealing with an elastic carrier-concentrator system. The functioning of the subscriber line equipment is described herein. The system serves 256 telephone subscriber lines by digital concentration switching and transmission of multiplexed message channels over a single T1 transmission line. The concentration switching function is nonblocking. Message channels are the individual communication links between terminals and are created on demand at the request of active subscriber lines. They are not merely inactive without service requests; they do not exist unless service is requested. The created message channels serve for their normal communication function and, in addition, carry for each line the ancillary functions of dialing, ringing, and pay-station coin disposal. Message channels are coded by delta modulation, which permits flexible digital concentration and provides a smooth tradeoff of channel quality versus the instantaneous traffic load. Each of two complementary subscriber line interface units, one per line at each end, provides the delta-modulation encoding and decoding functions for the analog voice-band signal input and output and, by overriding the delta codec, provides the desired signaling functions of dialing, ringing, etc. The line interface units provide the major equipment interface between the subscriber line and the digital T1 line. An integral test facility permits remote loop-back of any selected subscriber line unit via a test channel to the office terminals and at the same time connects the subscriber loop to an auxiliary programmed test facility which may transmit pertinent loop-test results to the office terminal.