THE FIRST VALVE

Evening Star, Issue 20990, 2 January 1932, Page 4

THE FIRST VALVE

Many years ago Edison was experimenting with electric lamps, trying to discover how the blackening of the inside of the bulbs came about in those of the old carbon type. He found that if a plate of metal was seated into the bulb and electrified positively, a current passed through the vacuum from tho filament to this plate. He noticed that the current always travelled from the filament to the plate; n'othingcould make a current pass in the opposite direction. He thought nothing of the discovery, and no use could be found for it, for it was many years before wireless was to be heard of. It was known as the Edison effect, and remained as a laboratory curiosity. Before anything can bo heard of wireless signals the waves must be rectified. Each wave consists of a push of current in one direction, followed by a pull in the other. .Rectification means straining out the pulls and leaving'only the pushes. All early methods of doing this were complicated and unsatisfactory. Then Professor J. A. Fleming had an inspiration. He made the first wireless valve in which a filament and a plate were placed in a vacuum inside a glass bulb. The Edison effect was harnessed, for the valve would respond only to the pushes and automatically eliminated the pulls. But' for the invention of the valve there would have been no broadcasting to-day.