Remove the battery cover. Connect the 9 volt battery to the connectors. Place the connected battery into the battery compartment and replace the battery cover.
Plug the transmitter into an electrical wall outlet with the power on to perform a unit test. Turn the receiver on until a click is heard and you see the LED lights to indicate the maximum sensitivity setting. Place the receiver near the transmitter to test the device. If the device is working properly you'll hear a beep approximately six times per second and the LED light will flash.
Plug the transmitter into a wall outlet with the power on to locate a circuit breaker or fuse that controls the wall outlet. Repeat Step 2 to test the unit. Locate your circuit breaker panel box. Place the flat surface of the tapered end of the receiver at a 90 degree angle and directly on the fuse or circuit breaker.
Move the receiver slowly up and down the row of circuit breakers or fuses. Constantly lower the receiver's sensitivity by turning the wheel away from the panel box until only one of the breakers of fuses causes the receiver to beep. Turn off the circuit after you have located the correct fuse or breaker to make the receiver stop beeping. Examine the red light on the transmitter in the outlet to make sure that it's off to confirm that you have turned off the correct fuse or breaker.
Turn a wall switch off if you'd like to see if that wall outlet is controlled by the wall switch. Plug the transmitter into the outlet. Perform a unit test as in Step 2. That portion of the outlet is controlled by the wall switch if the transmitter doesn't beep.