ECHOES IN WAR & PEACE

[Music] tied and all that happened in nature men saw the actions of gods and goddesses [Music] hello I am I am a coal [Music] according to the legend this maiden pined away leaving her voice to the rocks leaving her name to the phenomenon [Music] [Applause] [Music] [Applause] [Music] [Applause] [Music] [Applause] [Music] this is the story of echoes [Music] the story of how echoes were used during the war to betray the enemy and to warn of his approach a story that tells how sound underwater echoing from a submarine can betray its location [Music] a story that tells how radio echos have been used to disclose the position of an enemy hidden by fog or slope a story that tells - of how these radio echoes can spot enemy planes flying in darkness the story of echoes at war starts with what scientists have learned about sound sound is a wave motion traveling from particle to particle if you could see the vibrating molecules of air that produce sound they would look something like this here is a convenient representation of a train of sound waves hello hello hello the invention of the telephone showed how to make electrical ears to pick up waves of sound arrow arrow and to convert them into waves of electricity traveling in wires with instantaneous swiftness hello and the invention of the telephone also showed how to make electrical mouths to send out sound waves hello hello electrical waves like sound waves grow fainter the father they traveled hello hello to make them stronger telephone engineers developed electron tube amplifiers and the stronger electrical waves make louder sounds hello hello hello special sounds are needed when echoes go to war these sounds are made by an electron tube device called an oscillator the sounds are strengthened by an amplifier when these sound waves reach an electrical ear they are amplified and make a picture on another electronic device called an oscilloscope the sound waves cause a spot of light to jump on a cathode ray tube screen with devices like these echoes can be put to work when a wave pulse leaves the electrical mouth a spot of light starts to travel across the cathode ray tube when the yuckle returns the spot jumps the distance the spot travels will show how far away the clip is this echo method of measuring distance is very useful in finding how deep the water is below a ship the apparatus operates in much the same way as it does in air high-pitched sounds are used higher than we can hear although electronic devices make the tell-tale sounds audible for the convenience of the operator [Music] these supersonic sounds as they are called can be aimed in a narrow beam if they are set out sideways their echoes will disclose nearby ships submarines or even hidden rocks telling their direction and how far away they are [Music] here is where the supersonic waves are sent out and received [Music] the control apparatus is near the bridge and below decks is the complex equipment called sonar that uses supersonic pulses to detect objects underwater by means of echoed when on convoy duty sonar keeps a constant search for enemy submarines contact that means an enemy sub has been detected with sonar pointing the way battle stations are man and the destroyer heads for the submarine [Music] the depth charges are made ready to make sonar so vital to underwater warfare required a great deal of scientific work it took a lot of research and experimenting all the way from basic mathematics to tests out at sea [Music] [Music] in its development many organizations cooperated the naval research laboratory started at all years ago many commercial activities collaborated with the Navy in the development of sonar and then there were contributions by the National Defence Research Committee and the Bell Telephone laboratories research was intense and unrelenting it was not long before sonar emerged as a mechanism of great complexity and precision it was manufactured in quantity by the Western Electric Company where blueprints were transformed into incredible mechanisms like this where every sonar had to meet a series of rigid tests and where each had to give correctly this curious answer to carry on their research bell laboratories engineers built an artificial ocean in which to test this apparatus which sends out to supersonic sound the sounds come from an array of crystals [Music] many experiments led to the choice of these crystals which were grown for this special purpose artificially in chemical solutions [Music] as soon as a sonar was designed and a working model built it was put through its paces outdoors in a floating laboratory [Music] in ways like these Bell system engineers developed and manufactured a successful sonar for our fighting forces many careful tests proved its efficiency and so did the real thing [Music] fire two [Music] sonar uses echoes of sound an equally marvelous devices radar which makes use of radio waves each has its special applications sonar for underwater where radio waves cannot travel and radar for long distances through air where sound waves would soon fade out the radio waves passed through clouds or darkness and by their echoes can locate airplanes hidden from sight [Music] [Applause] from this antenna the radar sends out bursts of radio waves [Music] hundreds of times a second it's powerful transmitter shoots a pulse of waves out from the antenna after each pulse an ingenious electronic device automatically switches the antenna from the transmitter to a special radio receiver which will detect any returning echoes back again to the transmitter goes the antenna connection and each time a wave starts out a spot of light starts to travel on a cathode ray tube indicator when the echo was received the spot jumps the distance the spot travels measures the distance the echo has traveled and so tells how far away the plane is but radar like sonar not only measures the distance to hidden objects it also reveals their direction in its search for enemy planes the radar swings its antenna around sweeping the sky with a narrow beam of radio waves these waves travel about 1 million times faster than sound in air so fast at an echo can return almost before a plane can move or the radar antenna can revolve at the instant an echo returns the direction in which the antenna is aimed shows the direction of the hidden plane for at this instant the antenna is pointing to the echoing object [Music] using these radio echoes radar gets complete information about enemy targets and it gets this data fast and from many miles away [Music] [Music] so meeting plain information now leading point in formation after echos have disclosed the enemy the radar can be switched to operate automatically and to follow any single plane in its flight regardless of the number of other planes in the formation the radar can send its information about distance and direction to an electrical gun director like the one developed by Bell Laboratories and manufactured by Western Electric for Army Ordnance the radar keeps following the plane and continuously tells the gun director where it is and how far away the director instantaneously calculates in what direction to swing the anti-aircraft guns and at what angle to elevate them so that the shells will meet the plane in its flight commence firing commence firing the director also sets the fuse so that 15 or 20 seconds after each show has left the muzzle it will explode close to the plane the radar which operates this electrical gun director was developed for the Signal Corps there are many other types of radar each adapted to a particular purpose and each showing its information on direction and distance in the manner best suited to the special purpose [Music] [Applause] [Music] [Applause] [Music] [Applause] [Music] a single battleship for instance carries several different radars to locate attacking planes to locate enemy ships through fog or darkness to locate submarines when only their periscopes are above water and to control the fire of its big guns and of its anti-aircraft guns when attacking enemy ships or Shore positions it was with radar controlled gunfire that our Navy gave the Japanese Navy its first big surprise destroying six of its warships in night action that was off to Solomon Islands in October 42 the radars which located the Japanese cruisers had been made from designs of Bell Telephone laboratories by the Western Electric these companies began to concentrate their efforts on radar even before Pearl Harbor [Music] but the secret development of radars goes back many years to pioneering experiments in the United States Naval Research Laboratory early designs came from the Army Signal Corps laboratories with their radio locators British scientists made a most important contribution here in America our National Defense Research Committee set up a radiation laboratory at Massachusetts Institute of Technology for research on radar leading in the development of radar was Bell Telephone laboratories which had a broad experience in shortwave radio and had pioneered in developing many kinds of electronic devices it's electronic physicists worked on devices for use in radar developing things like the magnetron tube which is the electronic heart in the latest type of radar today's magnetron sent out much stronger pulses than did the earlier designs with which the [ __ ] warships were surprised back in 1942 [Music] this tiny magnetron for example sends out pulses as strong as those of a broadcast transmitter tube many times its size at its field laboratory in New Jersey their laboratory centers its development of complete radar systems here also each new model can be tried out and thoroughly tested [Music] here is a battleship fire-control radar getting a foretaste of seasickness [Music] this radar now undergoing laboratory tests is for a night fighting airplane the antenna and its reflector fly up in the nose of the plane to search the skies ahead the rest of this radar is all stowed away in the fuselage or mounted in front of the radar operator in the tail of the plane over the intercom telephone the operator keeps the pilot informed of what the radar sees the radar antenna sends its waves into the darkness ahead when echoing waves return they operate an indicator which shows the enemy's range or distance on its cathode ray tube [Music] [Music] the same radar may have two or more cathode ray tubes to give information in different forms when the enemy is spotted by the radar this other screen makes a picture now the enemy is to the left and above now our night fighter is flying in the right direction but still a little too low and now she's right on the target the enemy plane is dead ahead in the pilots line of fire [Music] many of these radars were shipped to England where the Royal Air Force and our own 8th Army Air Force used them to hunt down German bombers at night [Music] they also help to protect the American and British lines after the landing of the Normandy coast long-range bombers carry several types of cathode ray tube indicators to give the crew just the kind of information that needs there is an indicator which plots its information to make a map of what the radar sees a narrow slice of radio wave sweeps across the earth far below the plane [Music] their reflections bring back information which appears like this on the cathode ray tube indicator of course it takes training to interpret a radar map the operator must learn to read the map just as a doctor learns to interpret his x-ray pictures the map like picture makes a lot of difference when bombers cannot see their targets [Music] [Music] bombs away with radars like these our fighting men have bombed our enemies without regard to clouds or darkness the war is over the last bomb has fallen the guns have been silenced today the Marvel of radar is being applied to the problems and pursuits of peace once again radar is making its Maps through clouds and darkness but this time for a peaceful navigation in the air and on the sea Bell Telephone laboratories is still developing radars and the Western Electric Company is still making them but never again let us hope will these two organizations have to concentrate on instruments of destruction instead they can again devote their efforts to the continuous improvement of barrel system services [Music]