External Hot Desk Users, Personal Ring Groups, and Multi Device User Groups

Each call to a DN in a personal ring group counts as a call in the total system traffic. If a call comes in from an external trunk to a PRG with three members, then that call becomes three calls for purposes of calculating traffic performance (cph).

Only the one call that is answered counts as a completed call for purposes of traffic intensity (CCS or Erlangs), although all of the attempted calls do use a channel for a few seconds while in the ringing state.

The voice channels used during ringing state are important when counting the number of trunks that might be necessary to support this type of call traffic. Each external device that is called as part of a PRG requires one B-channel on a digital trunk while it is ringing, but when one line is answered all of the other voice channels are dropped. If a user has a desk phone and two external numbers in his PRG, then a call to him from the PSTN will use three B-channels while ringing (one incoming and two outgoing) and two if answered on one of the external phones (one incoming and one outgoing). A call from an internal user to that same person will use only two trunks while ringing, one if answered on one of the outside lines, and none if answered on the internal line.