Panasonic KX-TG5771BXS Service Manual page 55

8.1.6. RX-CW Test Mode for Handset
Note:
(*1) LCD displays the Channel number.
(exception: default/ CH00 = 1ch.)
(*2) Refer to Check Table for RF part (P.67) and Test Burst Mode for Base Unit (P.50) for proper Base Unit settings.
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KX-TG5771BXS/KX-TGA570BXS