Interlogix Recessed Door/Window Sensor TX-E221

you will need a small flat-head screwdriver insert the screwdriver into the notch on the cover of the device and pry it off gently remove the circuit board from the device locate the battery note that the battery can only be removed on one side due to the metal that holds it in place gently remove the battery note the battery terminals positive and negative place a new battery into the slot note the indents on the inside of the device replace the circuit board in the device by sliding it into the indents replace the cover on the device press in until you hear a click you