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1.3 System Features
Calling Party Control (CPC) Signal Detection
Description
The Calling Party Control (CPC) Signal is an on-hook indication (disconnect signal) sent from
the Central Office when the telephone is hung up at the other end. To maintain efficient
utilisation of CO lines, the system monitors their state and when CPC Signal is detected from
a line, the system disconnects the line and alerts the extension with a reorder tone.
Conditions
• This feature is enabled or disabled on incoming and outgoing CO calls separately by System
Programming.
• CPC Signal Detection on outgoing CO calls
Generally CPC Signal Detection works on incoming CO calls, and does not work on
outgoing CO calls (except once they are placed on Call Hold, Exclusive Call Hold or
Consultation Hold). In this case, if the extension user remains off-hook after the completion
of an outgoing CO call, the system does not release all the switches used to establish the
connection. The connected CO line will continue to be in use. To prevent this, it is
programmable to make CPC Signal Detection work on outgoing CO calls.
Note: Some Central Offices (CO) may send CPC-like signals during the dialling sequence
and an attempt to make a call may be terminated. If your CO sends such signals, it is
recommended to make CPC Signal Detection work on outgoing CO calls.
• Digits Restriction in CO Talk Mode
If your Central Office does not send CPC-like signals, it is effective to limit the number of
dialling digits permitted during a CO call by the programme "Digits Restriction in CO Talk
Mode" of Class of Service programming to prevent unauthorised calls.
• If a CPC Signal is detected during a Conference call, the line is disconnected and the
remaining two parties resume the call.
• If a CPC Signal is detected during a DISA call, the line is disconnected.
Programming Guide References
• 2.4 Class of Service (COS)
– Digits Restriction in CO Talk Mode
• 4.2 Trunk Line
– [CPC Signal] OUT Detection
– [CPC Signal] IN Detection
Features Guide References
None
User Manual References
Not applicable.
22
Features Guide
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