AT&T MERLIN LEGEND System Reference Manual page 227

Features
Forced Account Code
Entry
Multi-Function Module
Group Calling
Night Service
Paging
Park
Personal Lines
Pickup
Pools
Privacy
2-178 Forward and Follow Me
Telephones with Forced Account Code Entry assigned can forward calls only to
extensions and not to outside telephone numbers. The user hears a fast busy
signal if trying to forward calls to an outside telephone number.
The use of Forward (including Remote Call Forward) and Follow Me is not
recommended on an MFM beoause the user does not have an LED that
indicates when the feature is active.
An available calling group member is automatically logged out when calls are
forwarded to an extension or telephone number. If a calling group member logs
in while calls are being forwarded, Forward or Remote Call Forward is
automatically canceled. Calls cannot be forwarded to calling groups.
When a line/trunk programmed to ring into a calling group is assigned as a
personal line on a principal user's telephone, an incoming call received on the
personal line is not sent to the calling group if the principal user forwards calls to
an outside telephone number via Remote Call Forwarding.
When a station is a member of a Night Service group and Night Service is
activated, calls received at the station are forwarded to extensions by using
Forward and Follow Me but are not forwarded to outside telephone numbers
when Remote Call Forward is used.
Calls cannot be forwarded to a paging group. The line/trunk number used to
connect loudspeaker paging equipment cannot be used to forward calls to
outside telephone numbers.
Returning parked calls are not forwarded.
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 the Remote Call Forward feature), unless the outside line/trunk is a
loop-start line/trunk with an unreliable disconnect.
Pickup features cannot be used to answer calls being forwarded to an outside
telephone number.
A pool can be used to forward calls to an outside telephone number. The user
enters the pool dial-out code before the telephone number.
When calls are forwarded to an outside number while the system is dialing the
outside number, the Privacy feature is automatically activated and users who
share the personal line cannot join the call.