An invisible fence is both a type and a brand of fence that keeps your pet inside a confined area. When a family moves from their home, they often leave their invisible-fence wiring intact and install new wiring in the new place. This means the new owners already have the wiring for an invisible fence. If you just bought a home that has an invisible fence, you can use a portable AM radio to find the fence perimeter.
Make sure your invisible fence is plugged in and turned on. You should see an indicator light on the radio transmitter unit confirming this.
Find the radio frequency that your invisible fence is using. This usually is an AM frequency on the lower end of the spectrum. Check your fence instructions for the exact frequency. If the instructions are unavailable, turn on a portable AM radio near the fence transmitter. Search the AM stations until you have found the correct one. You will know you have it when you hear a fast-paced clicking or beeping sound.
Walk through your yard with the AM radio tuned to the correct radio frequency. Start around the perimeter because this is where invisible fencing is most likely be located. Also consider crisscrossing the yard to pick up any other invisible fencing that might be surrounding a particular area. Places where you hear a fast tapping or beeping from the AM radio are where the invisible fencing is located.