Signaling systems
Are essential as switching systems &
transmission systems
Must be compatible with switching
systems
Must be able to transmit all the signals
required to operate the switching system
Also be compatible with transmission
systems
, Compelled signalling
When continuous signalling is used, a
signal is sent until the acknowledgement
is received & acknowledgement signal
persists until original signal has been
removed.
Advantage – most reliable
Problem – when a circuit has long
propagation delay time, signaling is slow
, Channel associated signaling
Exchanges have sent signals over the same
circuits in the network as the connections
which they control.
Common channel signaling
Since signals are generated by central
processor in one exchange & sent to the
processor in another exchange, they can be
transmitted directly between processors.
, Customer line signalling
In a local telephone network there is a
minimum line current that exchange can
detect, thus there is a maximum permissible
line resistance. This limits maximum length of
line & area served by exchange.
In the case of dial telephones, customers needed
to send address in decadic pulsing. So a relay
circuit to receive dial pulses are required in
exchange.
Are essential as switching systems &
transmission systems
Must be compatible with switching
systems
Must be able to transmit all the signals
required to operate the switching system
Also be compatible with transmission
systems
, Compelled signalling
When continuous signalling is used, a
signal is sent until the acknowledgement
is received & acknowledgement signal
persists until original signal has been
removed.
Advantage – most reliable
Problem – when a circuit has long
propagation delay time, signaling is slow
, Channel associated signaling
Exchanges have sent signals over the same
circuits in the network as the connections
which they control.
Common channel signaling
Since signals are generated by central
processor in one exchange & sent to the
processor in another exchange, they can be
transmitted directly between processors.
, Customer line signalling
In a local telephone network there is a
minimum line current that exchange can
detect, thus there is a maximum permissible
line resistance. This limits maximum length of
line & area served by exchange.
In the case of dial telephones, customers needed
to send address in decadic pulsing. So a relay
circuit to receive dial pulses are required in
exchange.
