A button configured for this feature allows you to control your phone's mobile twinning operation. This is only useable if your system administrator has configured you for mobile twinning.

If pressed when the phone is idle, the phone displays the mobile twinning menu. You can use the menu to switch mobile twinning on/off and to setting the twinned destination.
If pressed while a twinned call is connected to the twinned destination, the system attempts to reclaim the call.
If pressed while connected to a call on the phone, the system attempts to transfer the call to the twinned destination. You do not need twinning switched on to use this feature.