AT&T MERLIN LEGEND System Reference Manual page 430

Features
System Programming
Related Features
In the Hybrid/PBX mode, a transferred call that returns to the principal station
does not ring on any of the Shared System Access buttons programmed for the
button on which the call is returning. If a transfer originator has a Shared System
Access button for the person receiving the transfer, the LED next to the Shared
System Access button flashes to indicate a ringing call. However, the call is
disconnected if the transfer originator answers the call.
Assign the Transfer Return Internal (0-9 rings, the factory setting is 4).
Options -> Transfer -> Return Time
Assign One-Touch Transfer with either automatic or manual completion or
One-Touch Hold. The factory setting is One-Touch Transfer with automatic
completion.
Options -> Transfer -> One Touch
Specify either Music-on-Hold or ringback for the Transfer Audible (the factory
setting is Music-on-Hold).
Options -> Transfer -> Audible
Select either System Access/Intercom Ring or System Access/Intercom
Voice for the Type of Transfer (the factory setting is System Access/Intercom
Ring).
Options -> Transfer -> Type
Camp-On
Transfer 2-381