Remote testing system for electrical circuits

Abstract From the Canadian patent

An apparatus for remotely testing electrical circuits such, as telephone circuits, includes a stand-alone unit which is located in the end office, for example for remote access by use, of an ordinary push-button telephone set sending dual tone multiple frequency signals. The apparatus has a twin-bus structure wherein one of the busses is an analog bus through which the telephone link is made and over which analog test signals are communicated; the other bus is a digital bus for communicating digital control and data signals with a microcomputer included within the apparatus. Operating between the two busses are suitable interface circuits for receiving the control signals from the telephone …