Note: You will need a small flathead screwdriver.
Before changing the battery of your device, please unplug the transformer.
Find the notches on the bottom corners of the device.
Place the screwdriver tip in the notches and pry off the cover.
Locate the two tabs at the top of the device. Lift both tabs at once to remove the device from the base.
Locate the battery.
Pinch the end of the wire and remove it from its connection.
Remove the battery.
Place a new battery in the device (Simon XTi Battery).
Connect the battery wires to their connection.
Replace the device on the base. Press in until you hear a click.
Replace the cover on the device. Press in until you hear a click.
After changing the battery, plug the transformer back in and reset the clock on the device.