This switch can be used to set the sensitivity of the sensor. This switch is used in situations when there is a chance of a false alarm due to heat sources such as radiators, small pets, etc. Setting 1 is the maximum sensitivity, setting 2 is a reduced sensitivity. 

One of the sensors or motion detectors has not contacted the base console for a long period of time. Check the batteries in the sensor or motion detector. Erase the zone and reregister the sensor. Move the sensor so that the signal can reach the console. If an error is found while setting the alarm, you will hear a repeated two-tone ‘error signal’. If a sensor indicates a problem (e.g. an open window), you can decide not to activate this sensor.
You need to press CLEAR while the error message is shown and then activate the alarm again. The zone indicator of the sensor concerned will now flash quickly.

You have pressed the CLEAR button to activate the security system while a sensor or motion detector has indicated a problem. Solve the problem (i.e. close the window, replace the batteries) before activating the zone. 

Marmitek does not have any specific sensors in the program. The system does however have 2 wired ins. You also have the possibility to connect a wired sensor to the DS90. Preferably use type NC (normally closed) wired sensors.