SPY=PROOF LAMP

Wairarapa Times-Age, 10 January 1940, Page 8

SPY=PROOF LAMP

USE OF POLARISED LIGHT. AGED SCIENTIST'S INVENTION. LONDON, December 16. Sir Ambrose Fleming, the famous scientist, has invented, at the age of 90. a simple and cheap spy-proof lamp for signalling from ship to ship and from ship to shore. The signals can only be read by the specially-equipped receiver for whom they are intended. Sir Ambrose, inventor of the valve that made broadcasting practicable, this week demonstrated, the lamp. He took the lamp and directed a finepencil of light at the eye of his assistant in the test, Mr J. D. S. Alan.

"I looked through a small tube," said Mr Alan. 1 “The light took a dark colour, then changed to steady, white dot-and-dash flashes as Sir Ambrose operated the shutter of the lamp from the opposite end of a corridor. If that pencil of light had been surrounded by code readers and spies they would have seen nothing. Only I with the tube could detect the flashings of the Morse code. If spies were very close to the lamp they would see only unbroken white light. "I was called in by the late Lord Fisher,” said Sir Ambrose, "to advise on this method of signalling in the last war. It was possible to use polarised light, but the crystals available were so small, rare and expensive that a simple projector and receiver would have cost hundreds of pounds. Now the complete apparatus can be made in large numbers for a few pounds.”