7
SIGNALING
7.1
WHAT IS THE PURPOSE OF SIGNALING?
The IEEE (Ref. 1) defines signaling as the exchange of information specifically concerned
with the establishment and control of connections and the transfer of user-to-user and
management information in a telecommunication network.
Conventional signaling has evolved with the telephone network. Many of the tech-
niques we deal with in this chapter are applicable to a telecommunication network that
is principally involved with telephone calls. With telephony, signaling is broken down in
three functional areas:
1. Supervisory
2. Address
3. Call progress audible-visual
Another signaling breakdown is
A. Subscriber signaling
B. Interswitch (interregister) signaling
7.2
DEFINING THE FUNCTIONAL AREAS
7.2.1
Supervisory Signaling
Supervisory signaling provides information on line or circuit condition. It informs a switch
whether a circuit (internal to the switch) or a trunk (external to the switch) is busy or
idle, when a called party is off-hook or on-hook, and when a calling party is on-hook or
off-hook.
Supervisory information (status) must be maintained end-to-end on a telephone call,
whether voice data or facsimile is being transported. It is necessary to know when a
calling subscriber lifts her/his telephone off-hook, thereby requesting service. It is equally
important that we know when the called subscriber answers (i.e., lifts her telephone off-
hook) because that is when we may start metering the call to establish charges. It is also
Fundamentals of Telecommunications, Second Edition, by Roger L. Freeman
ISBN 0-471-71045-8
Copyright
2005 by Roger L. Freeman
149
Summary :
7 SIGNALING 7.1 WHAT IS THE PURPOSE OF SIGNALING? Interswitch (interregister) signaling 7.2 DEFINING THE FUNCTIONAL AREAS 7.2.1 Supervisory Signaling Supervisory signaling provides information on line or circuit condition. It informs a switch whether a circuit (internal to the switch) or a trunk (external to the switch) is busy or idle, when a called party is off-hook or on-hook, and when a calling party is on-hook or off-hook.
Tags :
telephone,information,superisory,switch,subscriber,offhook,network,call,party,circuit,whether,roger,know