The tariff schedule divides relays into those for voltages not exceeding 60 V (853641) and those for voltages above 60 V but not exceeding 1,000 V (853649). The rated coil or contact voltage of the relay — as specified by the manufacturer — determines which subheading applies. This distinction affects duty rates and, for Chinese-origin goods, the applicable Section 301 list.

Connectors specifically designed for optical fibers, bundles, or cables classify under 853670 within this heading, regardless of the end-use application (telecom, data center, or industrial). The connector itself — not the cable or the system it connects — is the article being classified, and the heading text explicitly covers this type.