The complete system enables the properties of radio communications to be examined in terms of directionality, shielding, range etc., particularly as a comparison with other communication systems such as IR controllers, light, microwaves etc.
The system consists of a 433MHz low power transmitter and matching receiver. 
The transmitter sends out a variable audio tone and the receiver has a built-in loudspeaker. 
Each unit measures 90 x 60 x 20mm excluding aerials and requires a 9V PP3 battery.