Telecommunications Essentials

Signaling Systems

This section discusses the nervous system of the network: the signaling system. A great deal of information needs to be passed back and forth between the network elements in the completion of a call and also in the servicing of specialized features. Four main types of signals handle this passing of information:

• Supervisory signals— Supervisory signals handle the on-hook/off-hook condition. For instance, when you lift a telephone handset (that is, go off-hook), a signal tells the local exchange that you want a dial tone, and if you exist in the database as an authenticated user, you are then delivered that service; when you hang up (that is, go back on-hook), you send a notice that says you want to remove the service. A network ...