C 3 Features3-38 FeaturesCalling Party Control (CPC) Signal DetectionDescription The Calling Party Control (CPC) Signal is an on-hook indication(disconnect signal) sent from the outside line when the telephone ishung up at the other end. To maintain efficient utilization ofoutside lines, the system monitors their state and when CPC Signalis detected from a line, the system disconnects the line and alertsthe extension with a reorder tone.Conditions • CPC Signal Detection is enabled or disabled on incoming and outgoingoutside calls by System Programming.• Generally CPC Signal Detection works on incoming outside calls, anddoes not work on outgoing outside calls (except once they are placed onCall Hold, Exclusive Call Hold or Consultation Hold). In this case, ifthe extension user remains off-hook after the completion of an outgoingoutside call, the system does not release all the switches used toestablish the connection. The connected outside line will continue to bein use. To prevent this, it is programmable to make CPC SignalDetection work on outgoing outside calls. (Note: Some Central Officesmay send CPC-like signals during the dialing sequence and an attemptto make a call may be terminated. If your CO does not send suchsignals, it is recommended to make CPC Signal Detection work onoutgoing outside calls.)• If your Central Office does not send CPC-like signals, it is effective tolimit the dialed numbers during a call by the program [991] “COSAdditional Information”; Class of Service to prevent unauthorized calls.• If a CPC Signal is detected during a Conference call, the line isdisconnected and the remaining two parties resume the call.• If a CPC Signal is detected during a call between a caller using theDirect Inward System Access (DISA) feature and an extension or anoutside party, the line is disconnected.Programming ReferencesSection 4, System Programming[405] CPC Signal Detection Incoming Set[415] CPC Signal Detection Outgoing Set[991] COS Additional Information, Field (1)Feature References NoneOperation References Not applicable.
