A radio-frequency remote control works by sending a radio signal from a transmitter to a receiver, which activates motors inside the radio-controlled device. A radio-controlled toy helicopter, for example, only requires a single motor to make the rotors spin. A toy car usually has at least two motors: one to make the wheels spin, and one to turn the front axle side to side, steering the car.
The transmitter for a radio-controlled device is typically handheld. It uses a power source, such as a battery, and has controllers, such as joysticks or triggers. The simplest controllers are nothing more than an on-off switch. Others allow for left and right turns, forward and reverse and variable speed. Some radio-controlled airplanes use a small gas-powered engine to turn the propeller and a radio transmitter to control the wing flaps and steer the plane. Radio-controlled sailboats use the wind for propulsion and a radio transmitter to control the rudder. Most radio-controlled toys operate at either 27 or 49 MHz, frequencies allocated by the FCC for consumer devices such as toys and garage door openers. Toy manufacturers often make different versions of each model using different parts of the frequency spectrum, so that multiple toys can be operated in close proximity without interference between the transmitters.