Panasonic KX-TD500 System Reference Manual page 1450

3.29 Tone detector failure (DISA/AGC card)
Error Code
Possible cause of
the malfunction
Countermeasures
Note
A yxx
xx= 01 to 40 : Slot number
y= 1 to 4 : Port number
1) Tone detector failure
2) Defective tone receiving path from the faulty port.
Set the faulty port to OUS, enter the
port test command
Faulty
None
Replace the LPR card
End
15-E-32
Pass