There are two methods supported by the IMG 2020 to interwork Called Party Number digits. One method labeled Enbloc requires that all the Destination address information be included in the IAM,SETUP or INVITE. The other method is Overlap. The IMG 2020 supports Overlap Receiving where the destination address is contained in an IAM and SAM sequence of messages or a series of INVITES, each containing one or more destination address digits (ISDN = SETUP,INFO message sequence). The received digits are buffered until the configured minimum number of digits is received or other termination condition is met at which point the outgoing call is made with the destination address Enbloc.

Call Flow

Open

Configuration

Overlap signaling is enabled/disabled in the channel group pane. For information on configuring overlap signaling, refer to the Overlap Signaling (Sending) and Channel Groups topics.

Additional Information

Euro ISDN (E1)

When Overlap Signaling is enabled, the IMG 2020 will collect digits until one of the following termination conditions is met, and then send CALL PROCEEDING and attempt to route the call.

• Minimum # of Digits Received - The value chosen should be equal to or greater than the maximum number of digits expected

• Total Overlap Timeout

• T302 Timer Expiry (Wait for INFO ISDN Timer)

• Reception of an INFO message with a Sending Complete Information Element

• Reception of a SETUP message with a Sending Complete IE

• Inter SAM Timeout - The time the IMG 2020 will wait for an indication from its internal ISDN layer that an INFO message has been received. This value should be greater than 15 seconds. If the Inter SAM Timeout value is less than 15 seconds and expires before T302, the IMG 2020 will send CALL PROCEEDING and attempt to route the call with the digits it has at that point.

• If a call is received and T302 expires, Cause 28 will be sent to the network. Should you choose to make your Inter SAM Timeout smaller than 15 seconds you will attempt to process calls with most likely less than the number of digits you want. It is incumbent on the side that is sending you digits to send a Sending Complete IE to indicate the sending of digits is completed.

• Overlap needs to be enabled for inbound ISDN INFO digits only if the outgoing side is IP or SS7 ANSI.