We have used the Petsafe wireless fence, for the last 4 years, and it does the job. The only drawback is range; the farthest you can set it is 90' from the sending unit. Dogs learn quickly, as it has a warning beep prior to shocking. The batteries, for the collars, last about 2 months or so. We buy them in bulk from Amazon. A nice feature about this system is that you can add as many collars as you want, and you can take the whole system wherever you go. We take it with us camping (if there is electric hookups), set the range to 30', and the dogs never leave your sight.