Automatic bypass system for ring type local area network

Claim 1

In a local area ring network wherein a plurality of signal transmitting and receiving nodes, each including a transmission link switch operable in either a transmitting or a blocking condition, each of said nodes being connected to the next in a continuous series by a signal-conducting path having first portions including an individual node and input and output lines connected thereto, and second portions through which each of said first portion output lines is connected to the next first portion input line, an automatically operable bypass system for isolating one of said first portions from the remainder of said signal-conducting path in response to a failure within said one first portion while maintaining the continuous series connection of all parts of said network other than said one first portion, said bypass system comprising: (a) an activity detector (22) having an input connected (via 32) to said one node output line (14), and adapted to generate an output when signals are present on said one node output line; (b) a signal-conducting bypass line (41) for conducting signals from the node preceding to the node succeeding said one node without passing through said one first portion; (c) first means (23) operable in response to a control input to enable signals from either said bypass line or said one node output line to be transmitted to the input line (37) of said succeeding node; and (d) second means (21) connected to receive and detect inputs from both said activity detector output (via 33) and said one node input line (via 36), and operable to supply (via 35) said control input to said first means in response to absence of an input from said activity detector output when inputs from said one node input line are detected.