AT&T MERLIN LEGEND System Reference Manual page 310

Features
Personal Lines
Description
A personal line (also called direct facility termination) is an outside line/trunk that
is assigned to a button on one or more telephones. A personal line can provide
a user exclusive use of a specific line/trunk, or the line can be shared by a
maximum of 64 telephones. In the Hybrid/PBX mode, a personal line allows
users to receive outside calls without system operator involvement.
When a personal line is assigned to more than one telephone, the principal user
of the personal line can be assigned via system programming. Assigning the
telephone as the principal user has the following effects:
A principal user with Remote Call Forward can forward calls received on the
personal line to an outside telephone number.
Note: Using Remote Call Forward to forward calls to outside numbers does
not work on loop-start lines/trunks with unreliable disconnect.
Calls received on the personal line follow the principal user's Individual or
Group Coverage patterns unless the personal line is set to no ring.
A personal line can be selected to make or receive outside calls by pressing the
associated Personal Line button on a multiline telephone; dial-out codes are not
needed. When the line is in use, the green LED is on at all multiline telephones
that share the personal line. Inside calls cannot be made or received on a
personal line.
When an individual personal line is assigned to a Personal Line button on more
than one telephone, each user can join an in-progress call on which Privacy has
not been activated by selecting the Personal Line button with the call. A
maximum of two users can join an in-progress call (including conference calls)
for a maximum of three users on the same call.
In the Key mode, the factory setting for personal line assignment is that the first
1--8 lines connected to the system are assigned as personal lines on all multiline
telephones, including Multi-Function Modules (MFMs) connected to MLX
telephones. No personal lines are assigned to single-line telephones or tip/ring
devices connected to a 012 or 008 OPT module. For the Behind Switch and
Hybrid/PBX modes the factory setting assigns no personal lines to multiline
telephones, single-line telephones, or tip/ring devices connected to a 012 or 008
OPT module.
The factory setting for all modes of analog direct-line consoles (DLCs) assigns
the first 1-32 lines connected to the system as personal lines. For digital DLCs,
the factory setting assigns the first 1-18 lines connected to the system as
personal lines.
Personal Lines 2-261