AT&T MERLIN LEGEND Release 4.0 Feature Reference page 480

Feature Reference
When used after dialing is completed on an outside trunk, Recall sends a timed
flash to the host switch, the trunk is kept, the user hears a new outside dial tone,
and calling restrictions are reapplied. On an ARS call or a call on a rotary-dial
trunk, Recall cannot be used until dialing is completed. On a call made using
the pool dial-out code, Recall can be used during, as well as after, dialing.
Recall can be used only on loop-start lines.
Considerations and Constraints
Recall can be used to send a timed flash to the host switch only on a loop-start
trunk.
The Recall or Flash button sends a switchhook flash. It is not a "redial" button.
Mode Differences
Hybrid/PBX Mode
In Release 1.0 or 1.1, Recall cannot be used on any outside call made or
received on an SA button. In Release 2.0 and later, this restriction is removed.
A Recall signal from a single-line telephone accesses the communications
system's Hold, Conference, and Transfer features.
Key Mode
In Release 1.0 or 1.1, Recall cannot be used on any outside call made or
received on an ICOM button. In Release 2.0 and later, this restriction is
removed.
A Recall signal from a single-line telephone accesses the communications
system's Hold, Conference, and Transfer features.
Behind Switch Mode
If Recall is used on a call made or answered on the prime line, the timed flash is
sent to the host switch.
The fixed Conf, Drop, and Transfer buttons 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 to activate those features on the host.
Once this programming is done, these fixed buttons have no effect when
pressed during an inside call.
480
Recall/Timed Flash