AT&T MERLIN LEGEND Release 4.0 Feature Reference page 554

Feature Reference
Each Page button can be programmed to begin with any extension number that
is a multiple of 50 in the range of 0–9950. However, to expedite call handling,
the assignments should be sequential. The range starting with the lowest
extension number should be assigned to Page 1, the range starting with the
next higher extension number should be assigned to Page 2, and the range
starting with the highest extension number should be assigned to Page 3. You
cannot program individual buttons on a DSS.
Operator park zones must be included in the extension number range specified
for one of the Page buttons.
Each of the 50 DSS buttons corresponds to one of three extension numbers.
The specific extension number is determined by the Page button that the
system operator presses. For example, if the first extension number for the
Page 1 button is programmed to be extension 100, the DSS buttons and
associated LEDs on a single DSS correspond to extensions 100 to 149.
Remote Access Renumbering
The number assigned to the trunk can be reprogrammed and used (after
appropriate digit deletion and addition) as a remote access code. Users can
call in on a trunk, programmed to supply the remote access code, and reach a
system dial tone (barrier code entry may be necessary). From the system dial
tone, users can call an extension, call a calling group, call a trunk number (if
permitted), or make an outside call (if permitted). See "Remote Access" for
more information.
Logical IDs
A logical ID is a number that is associated with each connection on the
communications system. There is one set of logical IDs for extensions and one
set for lines/trunks.
Line/trunk logical ID's start numbering at the first jack of the first line/trunk
module in the control unit with the number 1 up to 80. For most line/trunk
modules there is a one-to-one correspondence between the jack and the logical
ID. The exceptions are:
Each 100D module is assigned 24 logical IDs, even though the
module has only 1 physical trunk jack.
Each 800 NI-BRI module is assigned 2 logical IDs per physical trunk
jack for a total of 16 logical IDs.
For extension modules, another set of logical IDs start numbering at the first
jack of the first extension module in the control unit with the number 1 up to 200.
For most extension modules there is a one-to-one correspondence between the
jack and the logical ID. The exception is the 008 OPT module is assigned 12
logical IDs, even though the module has only 8 physical extension jacks.
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System Renumbering