The radio transmitter is the pilot's link to the aircraft and houses the various sticks and switches for manipulating the control surfaces, engine throttle, retractable landing gear etc. Radio sets range from 2 channel to as many as 14 channels (each channel represents a separate function on the aircraft that can be controlled).

Modern radio units are usually programmable in some way to allow different setups to be stored for a number of different aircraft and often there are advanced control options such as high and low rates and various response curves that can be programmed differently for different planes.

For a powered plane 4 channels are required to fully control the aircraft; Throttle, Rudder, Elevator and Ailerons. More channels would be needed for features like flaps, retractable landing gear, smoke etc.

Helicopters use basically the same transmitter hardware but will have specialized programming options. A number of transmitters allow programming for both fixed-wing and helicopters enabling the use of the same radio unit with several very different aircraft.

The receiver unit, (often abbreviated as rx) resides inside the plane or helicopter and receives the radio signals from the transmitter and in turn drives the servos.

The servos (right) are small units housing an electric motor geared to an arm that connects via linkage and moves the control surfaces in direct proportion to the pilot's transmitter input.

All of these electronic devices are powered by different types of rechargeable batteries. In the case of a nitro powered plane or helicopter a small ni-cad (nickel cadmium) or li-po (lithium polymer) battery pack will power the onboard receiver and servos. In the case of electric powered craft a larger li-po pack is generally used for the main power and often some of this power is used to run the receiver and servos via a 'battery elimination circuit' or BEC to save weight and for simplicity of charging.