Technical information

MERLIN LEGEND Communications System
Issue 7 June 2001
5-9
Protection Via Star Codes and
Allowed/Disallowed Lists
Starting with MERLIN LEGEND Release 3.1, star codes can be added to Allowed
and Disallowed Lists to help prevent toll fraud. These codes are dialed usually
before an outgoing call, and they allow telephone users to obtain special services
provided by the central office (CO). For example, in many areas, a telephone user
can dial *67 before a telephone number to disable CO-supplied caller
identification at the receiving party’s telephone.
Whenever a user dials a star code, the system checks the Allowed and
Disallowed Lists to determine whether the star code is allowed. If the star code is
allowed, the star code is passed to the CO, the Calling Restrictions are reset, and
the digits following the star code are checked by the Allowed Lists, Disallowed
Lists, and Calling Restrictions.
The system recognizes star codes containing two digits ranging from either 00
through 19 or 40 through 99 (for example, *14). It also recognizes star codes
containing three digits ranging from 200 through 399 (for example, *234).
Therefore, for example, if a caller dials *67280, the system checks *67 against the
Allowed and Disallowed Lists. If this code is allowed, the system then checks 280
against the Allowed and Disallowed Lists.
Multiple leading star codes (such as *67*70) are also handled by the system: the
dialed number is checked against the Allowed and Disallowed Lists after each star
code is detected.
The following table gives examples of how to allow and disallow calls via star
codes and Disallowed Lists.
Table 5-2. Allowing and Disallowing Calls via Star Codes and Disallowed
Lists
Objective Solution
Disallow calls preceded by *67, but
allow all other calls.
Enter *67 as a Disallowed List entry.
Disallow calls preceded by all star
codes, but allow all other calls.
Enter * as a Disallowed List entry.
Disallow calls preceded by either *67
or *69, but allow all other calls.
Enter *67 as a Disallowed List entry,
and enter *69 as a separate
Disallowed List entry.
Disallow calls preceded by *67, calls
to 900 numbers, and calls to directory
assistance (411), but allow all other
calls.
Enter *67, 900, and 411 as separate
Disallowed List entries.