Panasonic KX-TG6521BXB Service Manual page 33

9.1.5. Check Handset Transmission
Cross Reference:
Signal Route (P.13)
9.1.6. Check Handset Reception
Cross Reference:
How to Check the Handset Speaker or Receiver (P.56).
Signal Route (P.13)
9.1.7. Check Caller ID
Cross Reference:
Signal Route (P.13)
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KX-TG6521BXB/KX-TGA651BXB