Panasonic KX-TD500 System Reference Manual page 357

Programming
Conditions
System Programming
"Configuration-DN Assignment"
"Extension-Station (1/4)",
XDP
The DHLC card is required to use the XDP feature.
3-F-97
Reference
VT Dumb
10-C-3.00 11-C-3.00
10-G-1.01 11-C-24.00