AT&T MERLIN LEGEND System Reference Manual page 314

Features
Forced Account Code
Entry
Forward and Follow Me
Group Calling
Hold
Multi-Function Module
Music-on-Hold
Paging
When Forced Account Entry is assigned to a telephone and the user tries to dial
an outside call on a Personal Line button without entering the account code, the
telephone loses its dial tone.
When an extension is programmed as the principal user of a personal line, calls
received on the personal line are forwarded to an outside number (if the station
can use Remote Call Forward), unless the outside line/trunk is a loop-start
line/trunk with an unreliable disconnect.
While the system is dialing the outside telephone number to forward a call, the
Privacy feature is automatically activated and users who share the personal line
cannot join the call.
To allow all calling group members' telephones to ring when an outside call is
not answered within three rings, the lines/trunks programmed to ring into the
queue can also be assigned to buttons on group member telephones and
programmed for Delayed Ring. This does not work for inside calls, Remote
Access Calls, direct inward dialing calls, or if a delay announcement device is
assigned to the group.
If a person uses a shared Personal Line button to join a call in the calling group
queue, the call is removed from the queue. If a delay announcement is playing,
it is disconnected from the call.
If a call is received on a personal line and is transferred to another user who
receives the call on a System Access or Intercom button and puts the call on
hold, users who share the line cannot select the Personal Line button and pick
up the call. If the person who received the transfer and put the call on hold
cannot return to the call, another user must use the Line Pickup feature to pick
up the call (for example, a system operator can take a message and disconnect
the caller).
When personal lines are assigned or removed from the associated MLX
telephone, they should also be removed from the MFM when the device
connected is used to answer calls or provide supplementary ringing.
As a general rule, personal lines should be removed from MFMs unless the
device connected (such as a fax or a single-line telephone) requires a personal
line on which to make an outside call.
A line/trunk used for Music-on-Hold cannot be assigned as a personal line.
A line/trunk used for loudspeaker paging equipment cannot be assigned as
personal line.
Personal Lines 2-265