Panasonic KX-TD500 System Reference Manual page 345

Related Features 1.FWD (Call Forwarding) to Tie
Extension users can forward their calls to a Tie Line.
The tie line extension number must be programmed beforehand.
[References]
Call Forwarding to Trunk (Section 4-F-2.05, 5-D-2.05)
2.Call Transfer to Tie
Extension users can transfer a call to a distant location over the Tie Line
Network.
[References]
Screened Call Transfer to Trunk (Section 4-F-1.03, 5-D-1.06, 6-G-1.04)
3-F-85