9032.90 - Parts and accessories:

This HTS category, 9032.90, encompasses parts and accessories specifically designed for use with automatic regulating or controlling instruments and apparatus, which are further detailed in Chapter 90 of the Harmonized Tariff Schedule. These parts and accessories do not function as standalone regulating or controlling instruments themselves. Instead, they are essential components that enable the proper operation, maintenance, or enhancement of broader automatic control systems. Examples include sensors, actuators, relays, integrated circuits, housings, and connectors integral to these devices.

Distinguishing this category from its siblings, 9032.10 (thermostats) and 9032.20 (manostats), is crucial. While those codes classify specific types of complete automatic regulating instruments, 9032.90 is reserved for the constituent parts and accessories *of* such instruments, or indeed any automatic regulating or controlling apparatus falling under heading 9032 that doesn't have a more specific parts classification. The focus here is on items that are not end products but rather enablers of end products within the broader category of automatic control.

Within this "Parts and accessories" category, further subdivisions exist to refine classification based on the type of automatic regulating or controlling instrument the part or accessory is intended for. For instance, there is a specific breakout for "Of automatic voltage and voltage-current regulators," indicating that parts designed for these specific devices are grouped together. The existence of these subcategories allows for more precise tariff treatment by categorizing parts based on the sophisticated control systems they support.