Safety interlocking system for switch equipment - has relay coils coupled into bridge arm and logic preventing more than one relay operating

摘要

The safety interlocking system, for switching equipment prevents a second sequence of operations taking place after a first sequence has been selected. The coils (d1 etc) of the switching devices (relays) are located in one branch of a resistance bridge. - The bridge corners adjacent to these coils can be connected via key switches (b1 etc) to a voltage supply (P,N). Depressing the appropriate key operates the associated switching device whose contacts (d1.2. and d1.1. etc.) connect in or out various circuit components that prevent other switching devices being operated by the selection keys.