vacuum tube

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vac·uum tube

a glass tube from which the air has been removed, containing two or more electrodes, between which passes an electrical current or spark; used in the production of x-rays, or to control circuits. Previously in wide use, the vacuum tube has been supplanted by transistors in electronic circuits.

vacuum tube

A vessel of insulating material (usually glass) that is sealed and has a vacuum sufficiently high to permit the free flow of electrons between the electrodes that extend into the tube from the outside. In England, it is called a vacuum valve.

vacuum

a space devoid of air or other gas.

vacuum collection
use of a handheld vacuum to recover ectoparasites from the coat of animals.
vacuum-dehydrated
freed of moisture while in a vacuum. Used in the packaging of food.
vacuum gauge
pressure gauge in a milking machine which indicates the level of vacuum in the system.
vacuum pack
meat or other perishable food is packed in a tightly sealed bag made of copolymers with polyvinyldene chloride and a low vacuum created. A bag made of nylon-polythene laminate is used for bags that are heat-sealed and a high vacuum created. The pack is then frozen for storage or shipment.
vacuum pressure
used as the basis of the modern milking machine; the negative pressure is generated by a vacuum pump and transmitted through metal and rubber pipes to the teat cups and thence to the teats; the continuous basic pressure is what keeps the teat cups on the teats; the periodic fluctuations is what causes the squeezing of the teat walls and the expulsion of the milk from the teats.
vacuum therapy
see cupping.
vacuum tube
many clinical pathology specimens are now collected in evacuated test tubes. A needle connected to the tube through a rubber stopper is passed into a vein. The needle is then connected to the vacuum and the blood or other fluid withdrawn.