Ideal for use in remote areas where an electrical power source is not available. Self-contained battery recommended for single-wire clean fence. Good output and convenient. DS20 - Controls up to 3 acres of clean fence. Outperforms competitor energizers rated at 3 miles. 0.07 joule output; 6 volt. DS40 - Controls up to 40 acres of clean fence. Recommended for cattle, horses, pigs, dogs and garden animals. Outperforms rival 10 mile solar energizers. 1 joule output; 12 volt.