Panasonic KX-TD500 System Reference Manual page 1443

3.22 Card type error (LPR)
Error Code
Possible cause of
the malfunction
Countermeasures
Note
21xx.
xx= 01 to 40 : Slot number
1) Assigned card type doesn't correspond to the installed card type.
Change the card assignment or
replace the installed card with
correct one
Enter INS command from the
maintenance terminal
None
15-E-25
End