Abstract: A system for tracing a conductor connected between a terminal of one terminal block and a terminal of another terminal block within a network of conductors and terminal blocks includes a supervisor associated with each terminal block for imposing a trace signal selectively on any of the terminals of said block. The supervisor also detecting a trace signal appearing on any of said terminals. A controller communicates with the supervisors to cause a selected supervisor to impose a trace signal on one of the terminals of its associated terminal block, and receives from the supervisors a report of another terminal at which the trace signal appears.