Emergency transfer circuit for use in a communication switching system

Claim 1

In combination with a communication system having a toll switchboard connectible through a switching network to an outgoing trunk circuit extending towards a distant office and having transmission leads and signaling leads, an emergency transfer circuit for permitting an operator to extend a call to the distant office via a toll switchboard trunk circuit in the event of a malfunction in said switching network comprising first relay means operable upon seizure of said toll switchboard trunk circuit by the operator to couple the transmisSion leads of said toll switchboard trunk circuit with said transmission leads of said outgoing trunk circuit, second relay means operable by the operator after the operation of said first relay means to open the signaling leads of said outgoing trunk circuit to thereby indicate a disconnect and hence cause the switch train in the distant office to release, said second relay means further being operable to couple one of the signaling leads of said outgoing trunk circuit to a third relay means, the distant office upon switch train release, causing return of a signal on said one signaling lead to operate said third relay means, said third relay means in operating connecting the signaling leads of said outgoing trunk to the signaling leads of said toll switchboard trunk circuit for use by the operator in extending the emergency call.