Made on behalf of the Bell System by Willard Pictures (2:25), ECHOES IN WAR AND PEACE focuses on principles of radar and sonar. The focus of the film is on the use of sound waves for detection and other purposes, including how sound is used underwater in order to track submarine locations (3:18). These echoes could pinpoint planes flying in the night sky (3:39). Scientists deduced that sound is the wave motion traveling from particle to particle (3:50). A representation of what sound waves might look like is shown (4:08). The telephone was able to pick up sound waves and convert them into waves of electricity which were able to travel through wires (4:23). However, the farther the waves had to travel, the fainter the sound (4:48). This lead to the introduction of electron tube amplifiers (5:00). During war time, special sounds made by an electron tube device called an oscillator were required (5:18). The sound waves would then cause a spot of light to appear on a cathode ray tube screen (6:05). How high the spot moved showed how far away the object was (7:14). Sonar is used to search for enemy ships (8:52). Much of the research for the equipment shown in this film was conducted at Bell Telephone Laboratories (10:11). Western Electric Company manufactured the bulk of the equipment (10:26). An artificial ocean created by Bell laboratories is shown (10:49) which was used for equipment testing. More tests are completed on a floating laboratory (11:36) and bombs are seen exploding under water (12:43). Radar, which makes useful of radio waves that travel through darkness and clouds (12:51), is used for monitoring planes in flight. The antenna which sends radio waves out is shown (13:26) as well as a diagram which points out the location of the transmitter (13:42). The cathode ray tube indicator which manifested the spot of light that determined the location of the object follows (14:08). After the location has been discovered, the system was able to switch to automatic and continue to follow the plane’s flight path (15:53). Western Electric manufactured this electrical gun director for Army ordinance (16:04). The information received from it was relayed to the men operating the anti-aircraft gun (16:31) and this enabled direct hits (16:58). The battleship depicted (17:58) carried a variety of radars in order to identify enemy planes, ships and submarines. Bell Telephone Labs manufactured the radar that was used to attack Japanese warships off the Solomon Islands (18:34). The US Naval Research laboratory pioneered much of the early research (18:56). The Massachusetts Institute of Technology’s radiation laboratory is shown (19:19) and radar research was conducted here. The front door of Bell Telephone Labs is shown and inside, the magnetron tube had been developed (19:43). The magnetron sends out pulses that were equally as strong as a much larger broadcast transmitter tube (20:02). Models were tested in the Bell laboratory field in New Jersey (20:11). The battleship fire control radar is shown being tested with a simulator which created stormy sea conditions (20:31). In England, the Royal Air Force and Eighth Army Air Force utilized radar equipment to shoot down German bomber planes (22:53). The long-range bombers which carried cathode ray tube indicators are shown (23:25). This film draws to conclusion as viewers are informed that after the war had ended, research and testing would continue for radar and sonar in peace times (25:36).

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