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NEWSCIENCENEWSCIENCENEWSCIENCE Secret wireless communication Speaking of possible war uses of new sound apparatus, the "talking light", one of the most interesting things still in the laboratory experimental stage, offers an opportunity to develop secret wireless communication from the front lines to the rear. The talking light is an electric arc in which the flame acts as a loud speaker, and can be made to speak with almost the volume of a good dynamic speaker. The principle behind the phenomenon was discovered by the inventor of the elephone, Alexander Graham Bell, and Hammond V. Hayes, one of the early Bell System engineers. They ound that speech could be ransmitted by a beam of light, and also that when a telephone ransmitter was connected across he terminals of an electric arc between carbon rods the flaming arc would reproduce the words spoken into the transmitter. At the same ime, beams of light were sent out which could be used to transmit speech several miles. We have found that the light not only talks but that it is modulated by the voice current, just as the glow of a neon lamp is modulated by the signals reaching a television receiver. It is possible by using photoelectric cells to pick up the beam of modulated light to reproduce it directly at a distant point as spoken words. Such a system would be the last word in directional wireless, for no one could listen in save by inserting a photoelectric tube in the beam; and with the latter directed from the front lines toward the rear, the enemy could not eavesdrop. Audiences listening to some of my talks on our work at the Bell Laboratories have been mystified by the fact that, though I am constantly walking about the stage and no microphone is in sight, my voice At the other end of the trans- oceanic radio phone circuits, similar inverters reverse the process and the party at the other end hears normal speech. If there is another war, the speech inverter may revolutionise the secrecy problem not only in radio conversations but on the telephone lines at the front. For, by simply changing the cycle according to a pre-determined arrangement, the enemy would be unable to pick up and translate the message, even with a similar machine. Learning to speak a few words of he inverted language, so you can alk into a microphone and have hem come out of the inverter changed into intelligible English, is an interesting experiment. If, for example, you can say “Cyaneon Playfeen Acecilofin" into the ransmitter, the inverting telephone apparatus will repeat back "Illinois Telephone Association". There are always portions of the sounds that no human throat can master. Such a simple word as "company", for example, becomes "crink-a-nope’. "NEW USES for SOUND Using the mew tiling are dheren in the photo at the bede, oops is frost line trenches con cemimiinicane with rear wither danger of cavenktopping by enemy. Ray from talking arc Iam picked up by photocell anal tune formed iio voice by the amplifier. Using the new talking arc shown in the photo at the left, troops in front-line trenches can communicate with the rear without danger of eavesdropping by the enemy. The ray from the talking arc beam is picked up by photocell and transformed into voice by the amplifier. 52 ¢ NEXUS JUNE — JULY 2009 www.nexusmagazine.com