Abstract: An apparatus is described having the capability to selectively alert subscribers in a telephone party line system where different subscriber parties are alerted using different ringing configurations. Subscribers are identified as being a member of a party by the connection pattern used to interface the apparatus to the telephone party line. The apparatus comprises means for detecting whether a ringer signal received from the telephone line is meant to alert a given subscriber party, and means for coupling the ringer signal to subscriber alerting equipment when an appropriate ringer signal is detected.

Abstract: A microcomputer controlled apparatus and method for testing communication lines including circuits serving multiple functions in the measurements of line electrical and noise characteristics. A current divider, an analog to digital converter, a constant current source, various filters and an RMS-to-DC converter are used to perform A.C. and D.C. voltage and current measurements, resistance measurement and noise measurement. Capacitance measurement circuits and method utilize a buffer for isolating the capacitance on the wire measured from other capacitance sources.