Panasonic KX-TG5771BXS Service Manual page 65

10.2.7. Check the RF part
10.2.7.1. Finding out the Defective part
After All the Checkings or Repairing
1. Re-register the checked Handset to the checked Base Unit, and Regular HS to Regular BU.
Note:
(*1) HS: Handset
(*2) BU: Base Unit
10.2.7.1.1. Registering a Handset
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KX-TG5771BXS/KX-TGA570BXS