OTHER FUNCTIONS AND CONTROLSBacklightThe backlight of the RT300 is switched on automatically whenever any of the keys arepressed. The backlight will remain illuminated for approximately 5 seconds after thelast key press, except if you are changing the set point temperature – in this case, thebacklight will remain illuminated throughout the setting change process.The backlight will not illuminate if the RT300 battery is low.Battery StatusThe RT300 checks the battery voltage frequently during normal operation. If thebattery voltage is sensed as being low (this is normally when the battery voltage fallsto a level of around 2.6V), the low battery indicator will be displayed on thescreen.Although the digital thermostat will continue to operate normally at this stage, youshould replace the batteries as soon as possible to prevent any possible operatingproblems.Sleep ModeBy pressing both the UP and DOWN keys together, the RT300 will enter SLEEP mode.In this mode, all the RT300 functions will be paused to save battery power.While in SLEEP mode:• The LCD display will be blank.• All output from the thermostat will be turned off immediately.Press any key to wake up the RT300 and cancel SLEEP mode.RT300 INSTRUCTION MANUAL 11RT300 100X115mm_Layout 1 23/08/2013 09:09 Page 11