# Motion Sensor Activity Timer

With the release of our [Motion Sensor](/concepts/devices.md#motion-sensor), a new mode of operation is introduced, the Activity Timer. Similar to our [Proximity Sensors](/concepts/devices.md#proximity-sensor), an event is sent at a trigger, here when presence is detected by the sensor. However, the state does not revert until a set timer has expired.

## How it Works

The Wireless Motion Sensor uses Passive Infrared Sensor (PIR) technology to detect the presence of people in a room by measuring changes in infrared light intensity coming from people moving into the sensor's field of view. When the sensor detects presence it will send a `MOTION_DETECTED` event to the cloud and start a pre-set Activity Timer. If the sensor continues to detect the presence of people before the Activity Timer expires, the timer will restart. When the Activity Timer expires, the sensor will send a `NO_MOTION_DETECTED` event to the cloud.

Independent of occupancy events, the sensor will periodically transmit Network Status Events to the cloud containing connectivity information, so that the system can know that the sensor is online and functional.

![](/files/tH8G5Ii4bpOzkU1oxKRP)


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