This sets the interdigit timer used once the digits collected so far already match at least one pattern in the digit map, but where an additional digit could still change that match to a different, longer pattern; the gateway waits out this timer to confirm no more digits are coming before reporting the match. This is the mechanism that resolves ambiguity between overlapping dial plans, such as a 3-digit extension versus a 4-digit one sharing the same first three digits, and this timer's length is exactly what determines how long a call appears to hang after dialing a short number before the gateway commits to routing it. With this timer set to 3 seconds and a dial plan where '123' and '1234' are both valid patterns, dialing '123' would appear to pause for up to 3 seconds after the third digit before the gateway commits to routing it as the 3-digit destination, unless a fourth digit arrives first.