The Ring Alarm System Door Sensor is a white, wireless unit that operates on both battery and wall plug-in power sources. It features a 1ms response time and is compatible with Amazon Alexa for smart home integration. The sensor includes an alarm and can be authenticated with a password. With a sleek LED LCD display technology and a contrast ratio of 50:1, this door sensor is perfect for home surveillance. Its compact size makes it easy to install and its IP/Network surveillance technology ensures reliable performance. these are used door sensors. they functions when they were used. to refund no returns
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