The Electronic Speed Controller (ESC) is a very high efficiency, low resistance, high current switch. Many ESCs also incorporate a Battery Elimination Circuit to regulate a voltage to power the receiver or another device, removing the need for a separate Li-Po battery for this purpose, however, a word of caution. Most ESCs operate over a wide range of input voltages and come in various current capacities which are clearly marked on the outer cover. All ESCs have two wire inputs and three wire outputs. Simon Kirby's Open source firmware ESCs, which have been specifically designed and tuned for multi-rotors have recently found favour amongst RC enthusiasts who claim that they provide a faster response and smoother performance with greater efficiency. ESCs have many other built-in functions, most of which were designed for helicopter or fixed-wing aircraft use. The latest innovation in ESCs means that these can now be set-up in software, thus avoiding all the hassle and expense.