Overlap dialing is required by CAS signaled lines. Overlap dial provides for a longer time-out period between digits, also called the inter-digit timer. With overlap dial set to off, the gateway expects to receive the digits one right after the other coming in to this line with very little delay between digits. With overlap dial set to on, then the device waits up to about 2 seconds between digits.
Basically overlap dialing is a mechanism where a destination number can be specified partially to complete the first stage of a routing path. For example, if the number was “23168104”, it may be possible for the telecom to dial “23168” to reach the first port of call as quickly as possible (to save time on sending the remaining 3 digits) and then deliver the remaining 3 digits “104” in overlap mode.
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