3Com 3C10402B Administrator's Manual page 267

Dial Plan Tables 267
digits of the extension. If the caller dials fewer than the Min number of
digits, the system times out in 20 seconds.
Example: If Digits = 2, Min = 4, and Max = 4, the system knows that if
the first digit is 2, it must collect no less than 4 and no more than 4 digits
before making the call routing decision.
If the caller dials at least the minimum number of digits and not more
than the maximum number of digits, the system waits 5 seconds and
then routes the call based on the digits the caller dialed. If the caller dials
more than the maximum number of digits, the system attempts to place
the call.
Often, the Max and Min values are identical, because you want the
system to collect a specific number of digits, no more and no less.
Example: For internal extensions, you want the system to collect exactly
3 digits (4 in a 4-digit dial plan) before it makes a determination. Set both
Min and Max to 3 (4 in a 4-digit dial plan).
The two columns might be different if the table entry applies to more
than one situation.
Example: In the United States, the Min value for the 90 entry is 2,
because 90 allows an internal caller to reach a telephone company
operator (9 to get an outside line, and then 0 to get the operator). The
Max value is 64, because the caller can continue to dial after the zero,
enter a number to call, plus a telephone credit card number, and possibly
an identification code number.
If the caller dials only 90 (which satisfies the minimum of two digits) and
stops dialing, the system waits for 5 seconds. If the caller does not dial
other digits, the system connects the caller to the operator.
If the caller dials other digits, the system accepts them up to the limit
of 64. If the caller stops after dialing fewer than 64 digits, the system
again waits 5 seconds before it acts on the dialed sequence of digits.
Example: You can assign a new employee to the Default User Group.
You can then set the permissions for that group so that group members
have permission to make LongDistance calls when the system mode is
Open or Lunch, but not when the system mode is Closed or Other.