MULTIPARTY LINE ADAPTER WITH PRIVACY CHARACTERISTIC

摘要

A circuit for adapting a telephone subscriber line to operate as a multiparty line is described wherein a plurality of conventional single line subscriber subsets are provided telephone service on the subscriber line such that each subscriber has privacy at all stages of call progress. In accordance with another feature of the present invention, frequency selective ringing is not required to prevent ringing from occuring at other subscriber subsets on the multiparty line when a party is called. The circuit of the present invention controls the switching of battery polarity at the central office to connect and disconnect subscribers from the line. The invention further provides automatic telephone number identification when calls are initiated by varying a unique identity tone for billing purposes. The invention also uniquely provides for user transparent reverting calling such that no special dialing procedure is required to make reverting calls and complete privacy is maintained, even on reverting calls.