An underground dog fence consists fo a buried wire, transmitter and dog collar with receiver. A great place to find a large selection of this type of fence is at Kozydogs.com they have every type of dog fence from the standard type to stubborn dog to small dog and a whole lot more.
The boundary wire is usually buried about to 2 to inches below the surface of the ground. Flags are placed in strategic locations to give you and the dog a visual location of the wire perimeter. The dog wears an electronic containment collar, which has a receiver that detects when the dog is getting to close to the boundary wire of the underground fence . It is at this point, the receiver gives an audible warning tone. If the dog keeps going towards the wire of the electric fence , then the collar will emit a mild electric shock to get the dog's attention, and htis is not at all harmful. This type shock can be compared to static electricity you get from your carpet. The stimulation increases as the dog keeps going towards the boundaries of the dog fence, until the dog stops and retreats. This way, the dog quickly learns to stay within the boundaries of the wire dog fence.
The installation of the wire electric dog fence system involves laying the wire around the area to be contained, above the ground. Then dig a thin, shallow trench in the ground to lay the wire in, and tap the edges of the dirt back over the wire. The fence kits sold at Kozydogs.com come with everything you need for your underground fence. The wire has to be a closed loop, any obstacles in the way have to be run through or the wire made to run under existing cracks or drainage pipes to complete the loop of the dog fence. You can install the wire containment system to include the entire area of your yard, or only the backyard, or have double-loop installations that can be a little more costly. Diagrams for these can be found at Kozydogs.com. Some dog owners like to combine an electrical dog fence with a physical fence additional protection. Can't be too safe!