This set demonstrates the use of visible light for sending signals. It consists of a transmitter and receiver unit, each with two transmission channels, plus an optional optical fibre link for each channel. The transmitter unit inputs can be connected to mp3 players, radios, and other audio sources, and the receiver unit outputs can be connected to amplified loudspeakers. Each unit has two monitoring points for use with a computer running sound analysis software. Includes two power supply units.