Electrical Symbols — Electron Tubes
Invented in 1904 by John Ambrose Fleming, vacuum tubes were a basic component for electronics throughout the first half of the twentieth century, which saw the diffusion of radio, television, radar, sound reinforcement, sound recording and reproduction, large telephone networks, analog and digital computers, and industrial process control. From the mid-1950s solid-state devices such as transistors gradually replaced tubes. However, there are still a few applications for which tubes are preferred to semiconductors; for example, the magnetron used in microwave ovens, and certain high-frequency amplifiers.
Pic. 1. Electron Tubes Library
ConceptDraw DIAGRAM is a powerful software for creating professional looking electrical diagram quick and easy. For this purpose you can use the Electrical Engineering solution from the "Engineering" area of ConceptDraw Solution Park.
Electrical Engineering Solution for ConceptDraw DIAGRAM provides the stencils libraries of ready-to-use predesigned 926 vector symbols, templates and samples that make your electrical drawing quick, easy and effective.
26 libraries of the Electrical Engineering Solution of ConceptDraw DIAGRAM make your electrical diagramming simple, efficient, and effective. You can simply and quickly drop the ready-to-use objects from libraries into your document to create the electrical diagram.
Pic. 2. Electrical Engineering symbols
Electrical diagram software will assist you in drawing your electrical diagrams with minimal effort and makes it very easy for beginners. Electrical symbols and smart connectors help present your electrical drawings, electrical schematic, wiring diagrams and blue prints.
Pic. 3. Electrical Symbols — Electron Tubes
Most of the electrical symbols can be changed in their appearance, styles and colors according to users' requirements. Electrical symbols are used to represent various electrical and electronic devices in a schematic diagram of an electrical or electronic circuit.
The following table lists some electron tubes electrical symbols in our electrical diagram software.
| Symbol | Meaning | |
| Electrical Symbols — Electron Tubes | ||
![]() | Diode, directly heated | |
![]() | Diode, indirectly heated | |
![]() | Diode, envelope, direct. heated | |
![]() | Diode, envelope, indirect. heated | |
![]() | Triode, directly heated | |
![]() | Triode, indirectly heated | |
![]() | Triode, envelope, direct. heated | |
![]() | Triode, envelope, indirect. heated | |
![]() | Tetrode, directly heated | |
![]() | Tetrode, indirectly heated | |
![]() | Tetrode, envelope, direct. heated | |
![]() | Tetrode, envelope, indirect. heated | |
![]() | Pentode, directly heated | |
![]() | Pentode, indirectly heated, external connection | |
![]() | Pentode, indirectly heated, internal connection | |
![]() | Pentode, envelope, direct. heated | |
![]() | Pentode, envelope, indirect. heated, external connection | |
![]() | Pentode, envelope, indirect. heated, internal connection | |
![]() | Diode, directly heated 2 | |
![]() | Diode, indirectly heated 2 | |
![]() | Diode, envelope, direct. heated 2 | |
![]() | Diode, envelope, indirect. heated 2 | |
![]() | Triode, directly heated 2 | |
![]() | Triode, indirectly heated 2 | |
![]() | Triode, envelope, direct. heated 2 | |
![]() | Triode, envelope, indirect. heated 2 | |
![]() | Tetrode, directly heated 2 | |
![]() | Tetrode, indirectly heated 2 | |
![]() | Tetrode, envelope, direct. heated 2 | |
![]() | Tetrode, envelope, indirect. heated 2 | |
![]() | Pentode, directly heated 2 | |
![]() | Pentode, indirectly heated, external connection 2 | |
![]() | Pentode, indirectly heated, internal connection 2 | |
![]() | Pentode, envelope, direct. heated 2 | |
![]() | Pentode, envelope, indirect. heated, external connection 2 | |
![]() | Pentode, envelope, indirect. heated, internal connection 2 | |
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.
How to Create an Electrical Diagram Using Electron Tubes Library
- Open ConceptDraw DIAGRAM new document page.
- Select libraries from Electrical Engineering section.

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There are a few different ways to place an object into your drawing:
- Click on an object and then click on the document, at the place you want the object to be inserted.
- Perform a drag-and-drop from the library to your document.
- Double click on an object’s icon in the library to place an object in the center of your document.
- Select the Smart Connector tool
. To connect elements using this tool, drag the connector from one connect dot to another.You can use Layers to place connections on different layers.
- Result: Electrical Diagram.
















































