This system enables the basic properties of optical fibres to be investigated and the ideas then extended to demonstration of some of the principal scientific and commercial uses. The low-cost plastic fibre may be cut to any desired length with a sharp knife and does not require any special terminating devices. It is also completely non hazardous. The system comprises a transmitter a receiver (both built onto P.C. boards 120mm x 150mm) and a 25m length of optical fibre. 20m of this is intended for speed of light determination and long distance communication demonstrations.Additional items required:Smoothed Power Supply Unit (College PSU or similar)Power Amplifier LoudspeakerOscilloscopeHigh Resistance VoltmeterTechnical Specifications:Transmitter:Light source: High intensity red LED output at 630nm.Modulation: Internal or external. The internal modulation source is a 300kHz oscillator (normally used for the speed of light experiment).External modulation input: 0 to 2V d.c. linear up to 5V digital or a.c. coupled via external capacitor (not supplied).External modulation frequency range: d.c. to greater than 300kHz TTL compatible.Monitor output: 0 to 2.5V for connection to an oscilloscope or to measure the LED operating current.Power requirements: 5 to 6V smooth d.c. reverse polarity protected.Terminations Optical: simple push in connection for 1mm diameter optical fibres.Terminations Electrical: all connections by both 2mm and 4mm sockets.Receiver:Input: Solid state photo-detector.Output 1: d.c. to greater than 5kHz for connection to meters etc. and general analogue audio signals.Output 2: High speed digital output 0 to 5V from below 20Hz to above 300kHz.Controls: Two providing for zero-set and gain on output 1.Power requirements: 5 to 6V smooth d.c. reverse polarity protected (the transmitter and receiver may share the same power supply if desired).Terminations Optical: simple push-in connection for 1mm diameter optical fibres.Terminations Electrical: all connections by both 2mm and 4mm sockets.