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Chapter 4 Integration with PBX

4-3

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Non-Supervised

The line is released when IM1200 transfers a call under Non-

Supervised Mode.  The PBX should be configured to forward the call back to the VM
port when the extension is not available.  This mode allows IM1200 to untie its
resource and provides the best performance.  This is the recommended call transfer
mode.  There are two ways Non-Supervised call transfer can be achieved:

∎

In-Band DTMF String

IM1200 will check the In-Band DTMF String sent by the

PBX for the reason (Busy or Ring/No-Answer) the call is sent back. This
method requires the PBX be capable of sending In-Band DTMF Strings with
condition codes when forwarding calls back to IM1200.

∎

Busy Time Lag

Some PBXes send the same In-Band DTMF strings for both

Busy and No-Answer Call Forward. This method uses the time lag between
receiving the Busy and No-Answer Call Forward when the call is bounced back
from the PBX to determine the extension is Busy or No-Answer. This method is
only recommended for certain PBX models.

∎

Supervised

In contrast to Non-Supervised Mode, Supervised Mode does not

release the line when transferring the call. It instead holds and monitors the line
for the extension’s response. It then retrieves the call if the extension is not
available, or releases the line if the call has been picked up by the extension. This
mode will take up the most resource of IM1200’s, but will be the only mode
possible if the PBX does not provide any extension status information when calls
are transferred. There are two things IM1200 can use to monitor the call transfer:

∎

Call Progress Tone

IM1200 monitors the Call Progress Tones (CPT) when

transferring a call, and retrieves the call when the defined number of Busy
or Ringback tones are received, then proceeds to take the call to the
corresponding call flow.

∎

DTMF

Instead of Call Progress Tone, IM1200 looks for the DTMF Signal sent

by the PBX when transferring the call. It will retrieve the call and process it
according to the DTMF Signal it receives. Not all PBXes provide DTMF Signals
for extension status.

∎

Semi-Supervised

In the case the PBX provides an incomplete set of In-Band

DTMF Strings, Semi-Supervised Mode can be used instead of Supervised Mode to
free up some system resource.

∎

Busy Recall, Ring Release

IM1200 will first operate under Supervised Mode to

determine and retrieve the call if the extension is Busy. If the extension is not
Busy, the line will be released in the Non-Supervised Mode. This mode
requires the Busy CPT parameters in the Supervised mode and the In-Band
DTMF String for the No-Answer condition in the Non-Supervised mode be set
properly first.

∎

Call Pickup.

Similar to Busy Recall, Ring Release method, the call is

retrieved if it is Busy and released otherwise. IM1200 will then use the Call
Pickup function of the PBX to retrieve the call in a definite amount of time,
assuming the call is not answered.

To configure the Transfer Mode:

Choose

System Parameters > PBX Parameters.

A PBX Parameters dialog box

opens. Choose the

Transfer Mode

Tab.