An audio amplifier with approximate overall voltage gain of 60. Operates from power supply voltages of 9V to 12V d.c. smoothed and regulated. Supply connection is via a pair of colour coded 4mm sockets on the front panel and the unit is internally protected against incorrect power supply polarity.Output signals can be via the internal loudspeaker or can be fed to the pair of 4mm sockets provided. This allows amplified signals to be displayed on an oscilloscope or used to drive a separate speaker. A two-position switch is provided for internal speaker or signal output selection.Signal input is made via a pair of 4mm sockets on the front panel and a volume control is provided. The unit can be used for a wide range of experiments and demonstrations. Input impedance is 500k ohms (approx) and as such the unit can be driven directly from a crystal microphone, signal generator, radio headphone output etc.Housed in a robust ABS plastic case. Supplied with instructions.