. Get alerts straight to your smart phone any time a door or window is opened with the Ring Alarm Contact Sensor. Installation is simple – no need to call out an electrician – just stick some batteries in and use the self-adhesive pads to place it on your door or window frame. Also the two halves of the sensor can be placed up to a maximum distance of 1.27cm away from each other meaning they'll still work if you have a bit of gap between the door and the frame. And not only is it compatible with Amazon Alexa but it'll work even if the Wi-Fi is out because it uses Z-Wave wireless tech instead.Please note to use the Ring Alarm Contact Sensor you'll need to download the free Ring app which is compatible with all iOS and Android devices. You'll also need the Ring Alarm Security Kit (sold separately). Key Features . Smart sensor - get alerts when a window or door opensCompatible with Amazon AlexaUses Z-Wave wireless tech up to a distance of 76mEasy to install with self-adhesive pads and batteriesThe 2 sensor halves can be placed up to 1.27cm apart . Product Specifications . Dimensions (H)8.0 x (W)2.7 x (D)2.1 cmBridge Included No - Requires Ring Alarm Base StationInstallation DIYManufacturer Warranty 1 Year. .