Sharp UX-51 Operation Manual page 26

Ringer
1
Press the UP or DOWN key. (Make sure the SPEAKER key has not been
pressed and the handset is not lifted.)
The ringer will ring once at the selected level, then the date and time will
reappear in the display.
DOWN
2
If you selected RINGER OFF: OK?, press the START/MEMORY key.
Display:
UP
RINGER: HIGH
or
RINGER: MIDDLE
RINGER: LOW
RINGER OFF: OK?
START/MEMORY
Volume Adjustment
21