Automatic number identification in subscriber loop carrier systems

摘要

A subscriber loop carrier system using digital transmission techniques is disclosed in which remote subscriber loops include two-party lines equipped for automatic number identification. The calling party going off-hook causes an automatic number identification (ANI) test request to be sent to the subscriber location. The ANI response signal is then encoded and transmitted to the central station to indicate which party is initiating the call. The same test for automatic number identification is repeated for any substantial discontinuity in the central office loop current to obtain an updating of the automatic number identification information. Encoded pulse signals are used for both the ANI test request and the ANI response signal.