Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Electrical engineering and control panels

Terminal block

Also known as: Feed-through terminal, DIN rail terminal

German: Reihenklemme

In control panel building, a terminal block is a modular, insulated connection element mounted on a DIN rail that connects conductors, typically the internal cabinet wiring to field cables, using screw, spring or push-in clamps.

  • Control panels

In one sentence

A terminal block is a modular DIN rail connection element that joins cabinet wiring and field cables with screw, spring or push-in clamps.

Example

Field sensor cables land on terminal block strip X2 in the cabinet, from which the internal wiring runs to the PLC input modules.

How it applies

  • Engineering: Terminal blocks come as feed-through, ground (PE), fuse, disconnect, multi-level and sensor terminals. Ground terminals connect to the rail and are colored green-yellow. Terminal strips are designated (for example X1, X2) in the circuit diagram.
  • Installation: Use the conductor sizes and ferrules the terminal is approved for, and apply the specified tightening torque for screw types.
  • Documentation: Terminal plans show strip, terminal number, internal and external wiring. Keep them current after changes; they are the primary document for troubleshooting at the cabinet.
  • Maintenance: Retighten screw terminals where the manufacturer requires it, and check for discoloration that indicates overheating connections.

Terminal block vs. connector

A terminal block makes a fixed connection changed with tools. A Connector makes a pluggable connection. Pluggable terminal blocks combine both principles.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: IEC 60947-7-1, Low-voltage switchgear and controlgear — Part 7-1: Ancillary equipment — Terminal blocks for copper conductors

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

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