Separate channel signaling
From Free net encyclopedia
Separate channel signaling is a form of 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.
The same channels, such as frequency bands or time slots, that are used for signaling are not used for message traffic, in contrast to common-channel signaling.
An example is the Integrated Services Digital Network (ISDN) telephone system which in Europe uses two 64kbit/s B channels to bear traffic, and a 16kbit/s D channel to transmit control information in domestic/small business ISDN-2e provision, or 16 B channels and one D channel in the E1-equivalent primary rate ISDN offered to larger businesses.
This example is complicated by the development of additional services to run on the always-connected D channel, such as some credit card terminal services.
In-band and out-of-band are phrases sometimes used to convey the same concepts.
References
- From Federal Standard 1037C and from MIL-STD-188