Abstract: Techniques to transmit auxiliary data are disclosed. One technique includes generating a control signal from a video data enable signal and an auxiliary data enable signal, and combining an auxiliary data signal and a video data signal into a composite data signal using the control signal. Techniques to receive the auxiliary data are also disclosed.

Abstract: In a data-transmission route involving parallel (e.g. 8Mb/s) data-transmission systems each using a separate line pair, a common line pair, linking all terminal and repeater stations, is used for supervisory and control purposes (signals up to say 25 KHz) and each of e.g. 100 repeater stations (provided with a digital regenerator per data-line pair) has a single error-detection and a single interrogate/response signal circuit at the station. Additionally each repeater station has selection means for connecting the output side of any of the regenerators of the station to the error detector which is permanently associated with the interrogate/response circuit. After the identical setting of the selecting means at each repeater station (e.g.