8540 - Thermionic, cold cathode or photocathode tubes (for example, vacuum or vapor or gas filled tubes, mercury arc rectifying tubes, cathode-ray tubes, television camera tubes); parts thereof:
Sub-classifications
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8540 11
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8540 12
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8540 6000
Overview
Heading 8540 encompasses thermionic, cold cathode, or photocathode tubes, which are essential components in a wide array of electronic devices. This broad category includes vacuum tubes, as well as those filled with vapor or gas, such as mercury arc rectifying tubes and cathode-ray tubes. It is crucial to note that while Heading 8540 covers the tubes themselves, specific components or accessories not integral to the tube's primary function might fall under different headings within Section XVI.
This heading is distinguished from sibling categories by its specific focus on electronic vacuum and gas-filled tubes. For example, categories within Chapters 84 and 85 that deal with solid-state semiconductor devices (e.g., transistors, diodes) are distinct from the electron-emitting principles central to Heading 8540. Similarly, while other electrical equipment might utilize these tubes, the classification here pertains directly to the tubes and their immediate parts.
Within Heading 8540, further subdivisions refine the classification based on the tube's specific application and construction. Subheadings differentiate between cathode-ray tubes used for televisions and computer monitors, specialized camera tubes, and microwave tubes like magnetrons and klystrons. Other subcategories address more general types of "other tubes" and "parts" thereof, allowing for precise classification of a diverse range of thermionic and related devices.