signalling (SIG)

Signaling is the exchange of switching information that is used to control the transmission of useful signals. Signaling is part of signaling. This involves the establishment and termination of connections.

Signaling can be done directly in connection with the communication signal, but it can also be done on channels that are physically independent of the communication signal. If the signaling signal is transmitted on the same channel and the same physical transmission medium as the data, it is referred to as innerband signaling, as in the analog telephone network with the dual-tonemultifrequency(DTMF) and dual-tone multifrequency(DTMF) methods. The switching standard for innerband signaling is the C5 standard. If the transmission of the signaling data and the information data takes place on separate channels, then it is outerband signaling. Typical examples of out-of-band signaling in the D channel ofISDN are the 1TR6 protocol and the DSS1 protocol, as well as the No. 7 signaling system.

In the case of very complex signaling, where a wide variety of services are supported and signaling of the signaling channels is required, this is referred to as meta-signaling. This is used in B-ISDN signaling.