ST621TX INSTRUCTION MANUAL
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BACKLIGHT
The backlight of the ST621TX is switched on automatically whenever the Touch Ring is activated, or any of
the keys are pressed. The backlight will remain illuminated for approximately 6 seconds after the last key
press, except if you are changing settings within the Clock, Programme or Temporary Override modes – in
this case, the backlight will remain illuminated for 10 seconds after the last key press.
The backlight will not illuminate if the ST621TX battery is low, or if the Slide Switch is in the LOCKED
position.
SLIDE SWITCH
The Slide Switch has two positions: UNLOCKED and LOCKED. In the LOCKED position, the Touch Lock
indicator will be visible on the LCD, and it will not be possible to change the ST621TX settings. If you
are unable to change any thermostat settings, check that the Slide Switch is in the UNLOCKED position.