Go to the fuse box and trip the circuit breaker that supplies electric power to the room or hallway where the alarm pad is located. Verify that there is no electricity by trying to turn on lights or appliances before continuing.
Remove the screws from around the alarm pad, using a Phillips screwdriver. Place the screws in your pocket to keep them from getting lost.
Pull the alarm pad out from the wall. If there is a cover plate, remove the cover plate first. Pull the alarm pad from the wall.
Pull the wiring from inside the compartment the pad was covering out so you can see the screw-tab connectors. Twist off the screw-tab connectors and place them in your pocket for safekeeping.
Take a picture of the twisted pairs of wires with a digital camera so that you can reattach them later without difficulty. Separate the twisted pairs of wires from each other.
Place the alarm pad face down on a work surface. Open the battery compartment lid on the back. If there is a screw on the lid, loosen the screw first, using a Phillips jeweler’s screwdriver.
Remove the battery from inside the battery compartment; if a button battery is being used, insert the tip of a flat-edged jeweler’s screwdriver into one side of the battery to loosen it so you can grip it.
Place the replacement battery into the battery compartment so that the battery caps line up with the battery compartment contacts; if a button battery is being used, place the button battery into the battery contact with the same-labeled side (“+” or “-“) facing up as was the case with the button battery that was just removed.
Reattach the wires on the back of the pad around the wires coming out of the hole in the wall; use the picture taken on the digital camera to match the wires up correctly. Twist a screw-tab connector on each pair of twisted wires.
Push the wires into the hole. Place the alarm pad on the wall, over the hole, and reattach the screws; if there is a cover plate, place the cover plate over the alarm pad and then reattach the screws. Restore the electricity at the fuse box.