Ring trip detector for a solid state telephone line circuit

Abstract From the Canadian patent

A ring trip detector for a solid state line circuit is disclosed that includes, a logic interface circuit connected to a central controller. The logic interface circuit is arranged to receive signals from the central controller for applying an ac ringing current to the subscriber loop and to transmit status signals from the ring trip detector to the central controller. A resistor, connected to the subscriber loop through a ringing current conductor, detects and develops a differential voltage that is proportional to the ac ringing current. A voltage convertor circuit connected, to the resistor, divides down the differential voltage and converts the differential voltage to a ground …