Abstract: A single cable inter-facility link is provided using an IDU-ODU telemetry interface employing an encoder in the status transmit circuitry and in the control transmit circuitry which encodes the appropriate data by integrating Manchester encoding, a preamble and postamble, and on-off keying to create a unique data packet scheme which is compatible with any existing inter-facility link protocol and which does not interfere with the DC power or normal data traffic. Together with a simple receiver structure implementing an adaptive threshold detector that decodes the telemetry data, any kind of information can be communicated between the IDU and ODU over a single cable. Control of the ODU by the IDU via a bi-directional half-duplex or full-duplex telemetry interface allows the IDU to control the ODU settings.