8540.20 - Television camera tubes; image converters and intensifiers; other photocathode tubes:

This HTS category, 8540.20, encompasses television camera tubes, as well as image converters and intensifiers. These are specialized thermionic tubes designed to capture visual information by converting light into electrical signals for transmission or recording. This specifically includes tubes used in broadcast cameras, surveillance systems, and scientific imaging equipment.

It is important to distinguish this category from its sibling, "Cathode-ray television picture tubes," which are designed for displaying images, not capturing them. While both are types of thermionic tubes, their fundamental function is reversed. This category also differs from "Microwave tubes," which are primarily used for generating or amplifying microwave signals, and other more general thermionic tubes.

The subcategories within 8540.20 further refine the classification. "Cathode-ray tubes" under 8540.20.20 specifically refer to cathode-ray tubes designed for image capture purposes, such as those found in older broadcast cameras. The "Other" subcategory, 8540.20.40.00, is reserved for image converter and intensifier tubes, which amplify low light levels or convert images from one spectrum to another, but are not direct television camera tubes.