Panasonic KX-TD500 System Reference Manual page 207

CO ringing/CO Held
Call Reminder
Extension ringing/
Extension Held Call
Reminder
Callback ringing
Timed Reminder/
Doorphone ringing
See Section 3-B-13.00 "Distinctive Dial Tone" for details of dial tone.
See Section 3-B-14.00 "Distinctive Busy Tone" for details of busy tone.
See Section 3-B-15.00 "Confirmation Tone" for details of confirmation tone.
See Section 3-D-4.00
Programming
None
Conditions
None
Ringing Patterns
1 sec
250 msec
1250
250
500 500
1792
"Discriminating Ringing".
3-B-27