Panasonic KX-TD500 Installation Manual page 268

5.2.1 Card/Port Test (On-line diagnosis)
Error Indication Table
Loop current failure
Bell detection failure
PB Generator failure
Hook signal detection failure
Dial pulse failure
Speech path failure (CO→Extension)
Speech path failure (Extension→CO)
PB receiver 1 failure
PB receiver 2 failure
PB receiver 3 failure
PB receiver 4 failure
5-12 Utility
Error Message Description
Loop current was not detected.
Bell signal was not detected.
PB Generator is not functioning properly.
Hooking signal was not detected.
Dial Pulse signal was not detected.
Speech path (CO→Extension) is abnormal.
Speech path (Extension→CO) is abnormal.
PB Receiver 1 is not functioning properly.
PB Receiver 2 is not functioning properly.
PB Receiver 3 is not functioning properly.
PB Receiver 4 is not functioning properly.