device for the combination of a variety of import datenbitströmen in a single source bitstrom

摘要

A plurality of digital data streams are combined into a single bit stream by a multiplexer apparatus in which a first multiplexer circuit combines bits from odd-numbered channels into a frame interval which begins with a first type terminal control bit and has a second type terminal control bit midway in the frame. A second multiplexer circuit combines the bits from the even-numbered channels into a frame interval which begins with a complement of the first type terminal control bit and has the second type terminal control bit positioned at a location midway within the frame. The outputs of both multiplexer circuits are scrambled in order to improve the signal statistics and are interleaved in a simple gated OR circuit in order to provide a bit stream having a bit rate which is twice the rate at which either of the multiplexer circuits is operated. In response to a timing control circuit, the first type terminal control bit is positioned in a digit space adjacent to its complement and the two second type terminal control bits are positioned in adjacent digit spaces within the output bit stream. As a result, framing is achieved entirely by the terminal control bits with no assistance from framing bits, and the multiplex circuits operate at a rate equal to approximately one-half the output bit rate. The terminal control bits are utilized primarily to provide stuffing and parity information.