The advanced taser uses an 18 to 26 watt electrical signal that overrides the central nervous system to directly control the skeletal muscles. Earlier devices operate in the 5 to 14 watt range and may not be effective on subjects who are extremely goal-oriented or high on drugs or alcohol. The advanced taser sends out a series of electrical signals. These signals, called T-Waves, are similar in many respects to the electrical signals used by the brain to communicate with the body. The 18 to 26 watt T-Waves cause an immediate, uncontrollable contraction of the muscle tissue. They are capable of physically debilitating the subject regardless of his/her mental focus or pain tolerance. Taser International refers to the patented technology as Electro Muscular Disruption (EMD). According to Taser International, the optimum range for the advanced taser with the 21-foot air cartridge is 12 to 18 feet. The accuracy of the advanced taser is excellent, much better than other tasers. It aims just like a handgun, so as to contribute to improved accuracy. Using "worst case scenarios," two leading experts in cardiac safety found the advanced taser has no adverse effect on heart rhythms. The electrical outputs of the advanced taser fall well within the safe levels defined by international standards. The only real risks of physical injury associated with the use of the advanced taser are secondary injuries from falling or being hit in the eye with a probe.