This film “Echoes in War and Peace” was produced by the Bell System and Willard Pictures (2:25). The focus will be radar, sonar, echo’s and 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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