From the Manufacturer:
The Pro Educator 900 is a modern e-collar designed with safety in mind, novel features like maximum stimulation setting and lock and set protect from accidental overstimulation of the dog. This 1/2 mile range e-collar is loaded with unique features making it one of the most humane and effective dog trainer collars around. The PE-900 transmitter is especially well-suited for easy operation and is small providing stealth operation when the situation requires discreteness. Don't be fooled by the small receiver size 2" X 1.5" X1 " 2.4 ounces; this remote dog trainer provides plenty of stimulation for most dogs even normal temperament 150-pound dogs respond to our blunt stimulation. The unique COS (control of stimulation) technology provides very clean stimulation without the normal head jerking often found with other training collars. The boost feature is available to provide boosted stimulation from 1 to 60. The night tracking light is controlled by the dog collar transmitter, allowing the user to flash or continuously light up the collar receiver for locating your dog after dark. You can also turn on the lost transmitter beeper to help locate a misplaced transmitter. The PE-900 Pro Educator will turn a smart, stubborn dog into a genius. 100% Satisfaction Guaranteed.