Improvements to the telephone circuits for the signalling a appelextérieur intended to an apparatus occupied

摘要

955,672. Automatic exchange systems. B. SCIRETTI, and G. ACETI. May 23, 1960 [May 26, 1959; Dec. 1, 1959], No. 18160/60. Drawings to Specification. Heading H4K. A subscriber's line circuit includes a coil connected in the private wire in series with a condenser and coupled to a second coil in the talking circuit, so that an attempt by a final selector to seize the line when it is busy gives an audible signal to the subscriber.