Panasonic KX-MB1520FX7 Service Manual page 171

12.3.13.2. Detective ITS (Integrated Telephone System) Section
1. No 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 microphone and the telephone line (sending), or between the telephone line and the speaker (receiving). Check the
components at that point. Check Sheet(P.170) is useful for this investigation.
2. No pulse dialing
3. No ring tone (or No bell)
CROSS REFERENCE:
Check Sheet (P.170)
NCU Section (P.30)
KX-MB1520FX7/KX-MB1520FX8/KX-MB1520FXW/KX-MB1530FX7/KX-MB1530FXW
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