Self-healing loop communications system

Abstract

Primary and back-up closed loop unidirectional transmission lines transmit self-clocking data streams and null data, respectively, in opposite directions to a plurality of loop interface units (LIUs) connected to the primary and back-up lines. To protect against failure of the entire system due to a break in the primary and/or back-up lines or failure of one of the loop interface units, each loop interface unit can detect a signal loss on the primary or back-up transmission line and wrap signal flow to bypass the detected fault. After wrapping around a detected fault, an LIU then creates a failure on the non-failing line causing an analogous wraparound in the LIU on the other side of the actual failure. After error recovery, there is then a complete loop connecting all non-failing loop interface units, although it is twice as long as before the signal loss was detected. Also disclosed is an alternate embodiment in which a microprocessor and attached external device are interconnected to a similar loop structure.