Telephone line status circuit

Abstract From the Canadian patent

A circuit for detecting a first plurality of status signals on a multiplicity of telephone lines and generating a second lesser plurality of control signals, less than the first plurality in response, thereto. Predetermined ones of the control signals are transmitted via a multiplexing circuit to a comparator circuit. A digital-to-analog converter generates analog threshold voltages for application to the comparator circuit in response to receiving command signals from a microprocessor. The comparator circuit generates a third lesser plurality of output signals, less than the second plurality indicative of, the status of a multiplicity of remote trunk circuits connected to the telephone …