AT&T Merlin II Release 3 System Manual page 57

CONSIDERATIONS
3-28 MERLIN II System Features
Calls can't be forwarded to phones that have Do Not Disturb activated.
Voice announcements can't be forwarded.
Forwarded calls can be answered using Call Pickup or Auto Answer-All.
A call can be forwarded only once. For example, if phone A's calls are
forwarded to phone B and phone B's calls are forwarded to phone C, a
call that comes into A is forwarded only to B, not to C.
Call Forwarding and Follow Me can't be in effect at the same time on a
phone. Activating one feature removes the other automatically.
An originating phone can have only one destination phone. However, a
phone can serve as the destination for more than one originator.