Page:Jack Heaton, Wireless Operator (Collins, 1919).djvu/188

 terruptor, an electric motor to run it and the usual key, loose coupled tuning coil and condensers.

The receiver was of a later type and had both a crystal detector and a , the latter being the invention of of England who has been Marconi’s technical adviser for many years. This detector is really a small incandescent lamp bulb with not only a filament but a metal plate sealed in it. The filament is kept at a white heat by a current from a storage battery.

When the telephone receivers are connected to the hot filament and the cold plate electrodes, the high frequency currents that are set up in the aerial by the incoming electric waves are changed into direct currents and the varying strength of these act on the head-phones. This detector is very sensitive and needs no adjusting.

Many of the messages we sent and received were in straight English but nearly all the important ones, especially those for and from Washington, were in code, the purpose of which was to prevent any one else, except our officers, from reading them and this kind of mes