In the field of telecommunication, signalling (UK spelling) or signalling (US spelling) has the following meanings: The use of signals for controlling communications. In a telecommunications network, the information exchange concerning the establishment and control of a connection and the management of the network, in contrast to user information transfer. The sending of a signal from the transmitting end of a circuit to inform a user at the receiving end that a message is to be sent. Signalling systems can be classified according to their principal properties