Switching system using momentary onhook signalling in answered trunk to detect abandoned call

Claim 1

IN AN AUTOMATIC SWITCHING SYSTEM WHEREIN A CALLING CONDITION AT THE CALLING END OF A TRUNK IS EFFECTIVE TO CAUSE SAID TRUNK TO BE REGULARLY ANSWERED BY CONNECTING THE ANSWERING END THEREOF TO AN AVAILABLE ATTENDANT POSITION, WHEREIN A PRESCRIBED AMOUNT OF DELAY IN EFFECTIVE AN ATTENDANT CONNECTION CAUSES A CALLING TRUNK TO BE SPECIALLY ANSWERED BY TEMPORARILY CONNECTING THE ANSWERING END THEREOF TO A DELAYED ANSWER ANNOUNCEMENT CIRCUIT, AND WHEREIN THE ANSWERING END OF A SPECIALLY ANSWERED CALLING TRUNK IS SUBSEQUENTLY CONNECTABLE TO AN AVAILABLE ATTENDANT POSITION: (A) MEANS IN SAID TRUNK FOR INDICATING WHEATHER OR NOT SAID TRUNK IS IN A CALLING CONDITION AND WHEATHER OR NOT A SAID CALLING TRUNK HAS BEEN SPECIALLY ANSWERED; (B) SIGNALING MEANS IN SAID TRUNK SELECTIVELY CONTROLLABLE BY SAID INDICATING MEANS (1) TO APPLY AN ON-HOOK SIGNAL TO THE CALLING END OF A SAID UNANSWERED CALLING TRUNK AND (2) TO APPLY AN OFF-HOOK SIGNAL TO THE CALLING END OF A SAID SPECIALLY ANSWERED CALLING TRUNK; (C) MEANS FOR SIGNIFYING AVAILABILITY AND UNAVAILABILITY OF AN ATTENDANT POSITION; AND,