Intercept arrangement for key telephone systems

Claim 1

For use in a key telephone system having a plurality of outside lines and having an intercept recorder provided in common for said outside lines; a ring counting, transfer and intercept trunk circuit having terminations for individually connecting said circuit to a corresponding one of said outside lines and other terminations for connecting said circuit to said common intercept recorder; having first switching means effective after the receipt of a predetermined number of rings over said individual outside line for initiating extension of said line to said common intercept recorder; and second switching means controlled by said first switching means and in turn controlling said circuit so that one, and only one, complete message is returned to said outside line by said intercept recorder regardless of whether said intercept recorder is kept in use by calls incoming from another, or others, of said outside lines said second switching means comprising switchthrough means controlled by said intercept recorder only when said recorder is not transmitting a message, for completing an answering loop from the output of said intercept recorder to said outside line, preparatory to the return of said message over said answering loop; and said ring counting, transfer and intercept trunk circuit further including a locking connection causing said first switching means to be held operated under the control of said switchthrough means; and switching elements controlled by said first switching means for closing an independent signalling circuit to key telephones included in said key telephone system; whereby signalling of said key telephone is continued irrespective of the termination of ringing current transmission over said outside line upon completion of said answering loop.