Made by the U.S. Army in 1942 for radio and electronics technicians, this educational training film shows the diode and the duo diode vacuum tube including the electron sources in the tubes and the symbols which designate varying types. It also breaks down electron behavior in matter and the effect of plate voltage changes. A vacuum tube (:15) and a large water-cooled tube (:19) are shown to be what has enabled continuous progress in radio. A span of various types and sizes follow (:24). A pilot in the cockpit of a bomber aircraft uses radio transmissions in order to stay in communication with units of his squadron as well as with his base (:34). Copper is pointed to and this material is one of many which has conductive properties (:57). Glass is shown as it does not readily conduct electricity and is often used as an insulator (1:03). Voltage is applied to the piece of copper and current flows through it (1:24). Heat is used to accelerate the current (1:43). The filament of a radio tube is heated by electrical current to depict this same action in a tube (2:05). An open filament type tube follows (2:16). The cathode is pointed to which is the sleeve surrounding the tungsten wire (2:41). The plate of the vacuum tube is shown (3:31). A span of military transmitting and receiving sets follow (3:58) with a single radio tube shown as well (4:05). Specific symbols which categorize radio tubes are broken down beginning with the designation of a simple tube (4:23). When plates are left uncharged, electrons remain near the cathode (5:16) and these then move to the positive plate when it is charged (5:26). The space charge is pointed to which rests between the cathode and the plate (5:54). Vacuum tubes are presented in a variety of sizes as well as capacities (6:27). An experimental circuit heater of a tube is shown to be attached to an A battery (6:37) as the cathode and plate are attached to a B battery (6:44). An ammeter measures the current (7:21). The point of saturation is depicted as when the current can no longer be increased (7:55). This point is charted on a graph (8:29). A diode tube is used to apply direct current in radio installations (8:43). An alternator is attached to the plate in the cathode of the diode tube (8:50) resulting in a rectified current. Half wave rectification is demonstrated (9:51) using an alteration current in a circuit with multiple resistances. A crystal rectifier is then shown (10:04). The symbol for the duo diode tube is presented (12:21). This has two plates (12:28) and it is attached to a transformer (12:46). Variations in the current are known as ripples (13:50). A variety of the duo diode tubes follow (14:27) including simple, multipurpose and rugged transmitter tubes (14:32). Military receiving sets are shown in montage (14:41) which use small tubes. Within a radio installation the vacuum tube is the center of the equipment (14:46) and the film concludes on a shot of a radio tower which is used to transmit and receive signals (14:50).

A vacuum tube, an electron tube, valve (British usage) or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The simplest vacuum tube, the diode, invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grids.

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This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com