Electrical Symbols, Electrical Diagram Symbols

"In electronics, a vacuum tube, electron tube (in North America), tube, or thermionic valve or valve (in British English) is a device controlling electric current through a vacuum in a sealed container. The simplest vacuum tube, the diode, contains only two elements; current can only flow in one direction through the device between the two electrodes, as electrons emitted by the hot cathode travel through the tube and are collected by the anode. Addition of a third and additional electrodes allows the current flowing between cathode and anode to be controlled in various ways. The device can be used as an electronic amplifier, a rectifier, an electronically controlled switch, an oscillator, and for other purposes.
Vacuum tubes mostly rely on thermionic emission of electrons from a hot filament or a cathode heated by the filament. Some electron tube devices rely on the properties of a discharge through an ionized gas." [Vacuum tube. Wikipedia]
"The EL34 is a thermionic valve or vacuum tube of the power pentode type. It has an international octal base (indicated by the '3' in the part number) and is found mainly in the final output stages of audio amplification circuits and was designed to be suitable as a series regulator by virtue of its high permissible voltage between heater and cathode and other parameters. The American RETMA tube designation number for this tube is 6CA7. Russian analog is 6P27S (Cyrillic: 6П27C )" [EL34. Wikipedia]
This circuit diagram sample was redrawn from the Wikipedia Commons file: EL34 schematics (circuit diagram).gif. [commons.wikimedia.org/ wiki/ File:EL34_ schematics_ %28circuit_ diagram%29.gif]
The example "Circuit diagram - EL 34 schematics" was drawn using the ConceptDraw PRO diagramming and vector drawing software extended with the Electrical Engineering solution from the Engineering area of ConceptDraw Solution Park.

The vector stencils library "Design elements - Electron tubes" contains 36 element symbols of electron tubes.
Use it for drawing electrical schematics and electronic circuit diagrams.
"One classification of vacuum tubes is by the number of active electrodes, (neglecting the filament or heater). A device with two active elements is a diode, usually used for rectification. Devices with three elements are triodes used for amplification and switching. Additional electrodes create tetrodes, pentodes, and so forth, which have multiple additional functions made possible by the additional controllable electrodes.
Other classifications are:
(1) by frequency range (audio, radio, VHF, UHF, microwave),
(2) by power rating (small-signal, audio power, high-power radio transmitting),
(3) by design (e.g., sharp- versus remote-cutoff in some pentodes),
(4) by application (receiving tubes, transmitting tubes, amplifying or switching, rectification, mixing),
(5) special qualities (long life, very low microphonic and low noise audio amplification, and so on).
Multiple classifications may apply to a device; for example similar dual triodes can be used for audio preamplification and as flip-flops in computers, although linearity is important in the former case and long life in the latter.
Tubes have different functions, such as cathode ray tubes which create a beam of electrons for display purposes (such as the television picture tube) in addition to more specialized functions such as electron microscopy and electron beam lithography. X-ray tubes are also vacuum tubes. Phototubes and photomultipliers rely on electron flow through a vacuum, though in those cases electron emission from the cathode depends on energy from photons rather than thermionic emission." [Vacuum tube. Wikipedia]
The symbols example "Design elements - Electron tubes" was drawn using the ConceptDraw PRO diagramming and vector drawing software extended with the Electrical Engineering solution from the Engineering area of ConceptDraw Solution Park.