Initial power-up mode
When the thermostat starts up for the first time, all icons are lit for about three seconds before entering ON mode.
ON mode
In ON mode, the current room temperature, plus, minus and status icons (i.e., connection state) are displayed on screen. This mode allows you to adjust the temperature setpoint and switch between OFF and ON.
The 
icon shows if the setpoint is adjusted manually via thermostat or mobile application, and indicates if the thermostat is in manual mode. It disappears after the thermostat receives the next setpoint via schedule, scene and automation from the mobile application.
Protection mode (OFF mode)
The thermostat activates protection mode (OFF) when you touch the standby button in ON mode. OFF is displayed. If the temperature drops below 8 °C, the thermostat activates the heating output automatically until temperature reaches 8 °C.
In OFF mode, the present room temperature and state icons (i.e., connection state) are displayed. Switch to ON mode by pressing the standby button again.
Sleep mode
After 20 seconds of inaction, the thermostat enters sleep mode. The screen is turned off. Previous setpoint adjustment or operating mode (AUTO, manual or protection mode) works in the background. Wake up the thermostat by touching the standby button.