Here is described a simple process to 'put a voice on a sunbeam' and transmit it over a distance. It is a fascinating example of amplitude modulation of light using sound vibrations. It then describes how the modulated light is detected...

A simple demonstration is described which shows how a transistor works. By including the audience into the actual circuit and by lighting LED's it shows the potential of the simple transistor amplifier. The extension to two transistors -...