Panasonic KX-TD500 System Reference Manual page 569

Any extension directory number can be
programmed to each DSS button, and the
associated LED indicator for each button
provides a busy/idle indication of the
programmed extension. Various features can be
programmed to the DSS and PF buttons.
The assignment for the DSS buttons and PF
buttons are programmed and changed either by
the system programming or PITS station
programming.
Programming
System Programming
"Extension-DSS Console"
PITS Station Programming
PF (Programmable Feature) Button
Assignment
DSS (Direct Station Selection) Button
Assignment
Conditions
None
Reference
VT Dumb
10-G-2.00
11-C-25.00
11-C-27.00
11-C-28.00
Reference
13-C-2.00
13-C-3.00
4-I-23