Panasonic KX-TD500 System Reference Manual page 1454

3.33 OHCA not installed (PLC/HLC)
Error Code
Possible cause of
the malfunction
Countermeasures
Note
D yxx
xx= 01 to 40 : Slot number
y= 1 to 8 : Port number
1) In spite of assigning "OHCA" to "Yes" in the station programming, OHCA
circuit card (KX-T96136) is not installed.
No
Change the assignment
None
Do you use "OHCA"
Is the "OHCA" circuit
installed in the faulty port
Yes
Replace the LPR card
End
15-E-36
No
Install the OHCA card