Progress Indicator description value

Parameter group

Trunk Interface

Access level

Admin

Possible values

An integer value in the range of 0 to 255 corresponding to the hex value to be transmitted (as the Progress Description value, byte 4) in the Progress Indicator IE sent with the ALERTING message for an inbound call.

Defaults

-1 (disables the sending of Progress Indicator)

Explanation

In some ISDN trunk voice applications there is a requirement to play voice to a caller prior to the call being completely established. An example might be to say “to avoid being charged for this call please hangup now” prior to sending a CONNECT (when charging begins). Some ISDN switches require a Progress Indicator Information Element (IE) with the initial ALERTING message in order to allocate a voice path ahead of receiving a CONNECT message.

Some ISDN switches do not allocate a voice path until after a call has been connected (not until after a CONNECT has been received and call charging has begun). The result is that voice played by an ISDN application cannot be heard until after an inbound call has been answered.

The system parameter Progress Indicator description value in the Trunk Interface group has been added for use wit E1 Euro ISDN and E1 QSIG. This parameter has a default value of -1 but otherwise has an integer value in the range of 0 to 255 corresponding to the hex value to be transmitted (as the Progress Description value, byte 4) in the Progress Indicator IE sent with the ALERTING message for an inbound call. The default value of -1 disables the sending of Progress Indicator.

Note: The Progress Indicator description value system parameter is independent of the generic (field and lab only) Channel Group parameter Connect Voice Channel Before Answer. Both need to be set for voice to be heard before connect.