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A terminal block is an insulated component that provides a fixed, reusable point for joining two or more electrical conductors. IEC 60947-7-1 — the governing standard for terminal blocks — defines it as an insulating part carrying one or more mutually insulated terminal assemblies and intended to be fixed to a support, typically a DIN rail or mounting panel. Each terminal assembly ties together two or more clamping units — screw-type or screwless (spring/push-in) — on a common conductive part, so a single block can bridge, feed through, or distribute a connection.
Because the conductors are clamped rather than permanently soldered or crimp-spliced, wiring can be landed, disconnected, and re-terminated without disturbing the rest of the circuit — which is why terminal blocks are ubiquitous in control panels, distribution boards, and industrial machinery. Key ratings are the rated cross-section and rated connecting capacity (the range of conductor sizes accepted), the rated voltage, and the clamping type. Common variants include feed-through, multi-conductor, multi-level, ground, and test-disconnect blocks.
In the wire-harness and aerospace work covered by IPC and NASA standards, the functionally similar stud-and-lug assembly is generally called a terminal board or terminal junction module rather than a terminal block; the terms overlap in everyday usage.
