AT&T MERLIN LEGEND Release 4.0 Feature Reference page 485

Feature Reference
System
Access/Intercom
Buttons
Transfer
Recall can be used on a ringing or answered inside call made on an SA
or ICOM button. The call is disconnected and the user hears dial tone.
When the user is listening to a busy signal, Recall has no effect.
Either the user with the principal SA button or the user with a Shared
SA button who has joined a call can use Recall. In Release 2.0 and
later, Recall is available on an outside call on a loop-start trunk when
the call was made or received on the SA or Shared SA button.
A single-line telephone user with a Recall or Flash button can use it to
transfer a call.
In Release 2.0 and later, Recall can be used on a transferred outside
call on a loop-start trunk, because the transfer is received on an SA or
ICOM button.
In Behind Switch mode, the fixed Transfer button on an MLX or analog
multiline telephone must be programmed through system programming
to send a timed flash plus the code expected by the host switch to
activate transfer on the host. If use of the communications system's
Transfer feature is also desired, it must be programmed on an available
line button on each multiline telephone, using extension programming
or centralized telephone programming.
485
Recall/Timed Flash