8540.89.00.40 - Diodes, triodes and tetrodes

This HTS classification, 8540.89.00.40, encompasses diodes, triodes, and tetrodes that do not fall under the more specific categories of gas and vapor electron tubes (8540.89.00.20) or light-sensing tubes (8540.89.00.60). These are thermionic or cold cathode devices that control electron flow, with diodes typically having two electrodes (anode and cathode), triodes three (anode, cathode, and grid), and tetrodes four (anode, cathode, and two grids). Their primary function is amplification, switching, or rectification of electrical signals.

The distinction from sibling categories is crucial for accurate classification. Gas and vapor electron tubes (8540.89.00.20) are characterized by the presence of gas or vapor within the vacuum envelope, which plays an active role in their operation. Light-sensing tubes (8540.89.00.60) are specifically designed to detect and respond to light. Therefore, diodes, triodes, and tetrodes classified under 8540.89.00.40 are primarily vacuum-based or utilize a vacuum principle without significant gaseous ionization or direct light detection as their core operational characteristic.

As this is a leaf node within the HTS structure, there are no further subdivisions for diodes, triodes, and tetrodes. Classification at this level relies on the absence of specific operational characteristics that would place them in the aforementioned sibling categories. Examples of items that might fall here include high-frequency power diodes, specialized vacuum triodes used in radio transmitters, or tetrodes employed in audio amplification circuits, provided they do not contain significant gas or vapor or are not primarily light-sensing devices.