How do I replace the window/door sensor batteries?

There are two versions of the Calex door/window sensor, each with its own way of replacing batteries:

1. Without external push button:

1. Hold the door sensor with the reset button side up.
2. Carefully slide down the back plate of the door sensor to open it.

2. With external push button:

1. Press the external button.
2. This loosens the back plate so you can easily open the sensor.

After removing the back plate, you can easily replace the batteries.