Separate channel signaling

Separate channel signaling: Signaling in which the whole or a part of one or more channels in a multichannel system is used to provide for supervisory and control signals for the message traffic channels.

Note: The same channels, such as frequency bands or time slots, that are used for signaling are not used for message traffic. Contrast with common-channel signaling.

Source: from Federal Standard 1037C and from MIL-STD-188