Transfers from Extension to Extension
From ViciWiki
Handset Transfer of Live Calls
To Transfer live call from handset to an internal extension:
While on a live call ...
Press Flash (which is often the green "answer" button) Enter Extension Number Press # TALK (warn of impending transfer) Hang up.
The transfer is now complete ... they are talking to each other and you are off the phone available for another call.
On some systems, this is "##" (quickly) instead of or in addition to "Flash" (especially if there is no "flash").