Panasonic BB-GT1500 Operating Instructions Manual page 56

Programming
Setting the base unit ringer tone (BB-GT1540) f
There are 3 tones and 3 melodies.
1
Press {IP/TEL} repeatedly until the display shows the desired line (n or
m).
L You cannot set the ringer tone for both lines at the same time.
2
{^}
3
Within 10 seconds, press {<} or {>} repeatedly to select the desired tone.
L To stop ringing, press {STOP}.
Note:
L k If you subscribe to a distinctive ring service (such as IDENTA-RING), select
a tone (tone 1 to 3). If you select a melody, you cannot distinguish lines by their
ringers.
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