Optical window and door contact - opening sensor plus for Homematic IP with a long service life The Homematic IP window and door contact plus comes with two batteries that allow for a service life of around four years. The functional principle on the basis of an infrared light barrier means that an additional counter-contact on door/window frames is unnecessary. If the opening sensor is linked to a Homematic IP heating actuator - for example a radiator thermostat - the energy costs can be reduced by reducing the heating power when windows/doors are open during ventilation. The contact may also trigger an alarm siren when it is armed and unauthorised opening is detected. In addition, the Homematic IP app enables you to keep an eye on the opening status of the monitored doors/windows at any time and from anywhere. Features / compatibility - Homematic IP integrates the areas of indoor climate, security, fire and water protection, weather, lighting and shutter control - simply installed, s