An "electronic fence" is a boundary or barrier created using electronic devices such as sensors or wires. It is used to keep something or someone within a specific area and alerts if they try to cross the boundary. Full definition
Don't count on an underground electronic fence to keep him confined; the threat of a shock is nothing to a tough terrier who wants to go after something. (dogtime.com)
Some people prefer to use an underground electronic fence, but this type of enclosure doesn't prevent other animals from coming into your yard. (dogtime.com)
You can also use electronic fence to keep Rover out of flower beds. (canismajor.com)