Apparatus for supplying channel-control signals and maintenance signals in a serial data concentrator system

摘要

A data link (1000) multiplexes a large number of concurrently operating channel onto a single pair of fiber-optic cables (10 and 1010). A receiver (1004A) at one end of the links determines whether it is in sychronism with the signals that it receives over one of the cables (1010), and a transmitter (1002A) includes the result of that determination with the data that it sends to the other end if the link so that devices at the other end of the link can be caused to log off in response to extended lapses in synchronism at the first end. Each transmitter also sends an error count to the other end, and is responsive to a mode signal from the other end to reduce its signal power, so that maintenance personnel can perform many testing and diagnostic procedures from a single end of the link. A single integrated-circuit chip (1005A) receives data serially from a modularly expandable shift register (208) that has recieved the data in parallel, and the chip sends the data serially in a "reverse" order so that expansion of the shift-register length requires no change in the chip.