Dialogic 6.2 - Manual (Page 206)

Transferring Calls Using Release Link Trunk Transfer
November 2009 206
Once the network establishes a direct connection between the
originator of the first call and the final destination of the second call,
it sends DISCONNECT messages for both B1 and B2. The calls are
released on the board (and the board does not need to keep two
B-channels established), but the switch maintains the actual
connections between the originator and the reroute destination.
DISCONNECT=====>L3L4mDISCONNECT (B1)
DISCONNECT=====>L3L4mDISCONNECT (B2)
For more information about the messages, see Volume 5, Bfv API
Reference Manual.