Panasonic KX-FP81BX Service Manual page 75

2.3.7.2. DEFECTIVE ITS (Integrated Telephone System) SECTION
1. No handset and speakerphone transmission / reception
Perform a signal test in the ITS or the NCU section and locate a defective point (where the signal disappears) on each route
between the handset microphone and telephone line (sending), or between the telephone line and the handset speaker
(receiving), or between the microphone and the telephone line (sending), or between the telephone line and the speaker
(receiving). Check the components at that point. 2.3.7.1. CHECK SHEET(P.74) is useful for this investigation.
2. No pulse dialing
3. No ring tone (or No bell)
CROSS REFERENCE:
2.3.7.1. CHECK SHEET(P.74)
6.8. NCU SECTION(P.164)
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KX-FP81BX / KX-FP81CX / KX-FP82CX