Abstract: An apparatus for providing an intercom function on a telephone, without the need for an external power supply, having DTMF or pulse capabilities including an intercom operation device arranged for connection to a DTMF or pulse telephone line and to a DTMF or pulse telephone instrument. The apparatus includes a device for sensing an extension selection dual input from the DTMF or pulse telephone instrument and transmitting a corresponding extension address signal over the DTMF or pulse telephone line. Also included is an apparatus for sensing a received extension address signal from the telephone line, determining whether it corresponds to the telephone instrument to which the intercom operation apparatus is connected and, upon determination of correspondence, providing an extension selection ring output.