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Terminal Blocks - Headers, Plugs and Sockets

Terminal blocks, also known as headers, plugs and sockets, are specially designed electrical or electronic engineering devices to connect or terminate insulated wires and cables. These electrical connections are usually screw terminal blocks initially created for uses found in telecommunications for connecting incoming and outgoing lines during testing or repair. Although the technology and design of the terminal blocks have evolved during the past decades, their primary purpose has remained the same. In general, they act as a bridge between the wires and the circuit board allowing the isolation of the circuit, as well as providing physical and electrical protection to the wiring.

Application Field

Terminal blocks are commonly used to provide points of connectivity in industrial, telecommunications, IT, residential or commercial environments. These headers, plugs and sockets are typically used in applications such as terminal and relay blocks, motor connectors, switchgear, panels and equipment, automotive electrical connection equipment, data acquisition systems, electrical control and monitoring devices, or DC motor control systems. The screw and terminal blocks are smaller than traditional crimp joiners like lugs, splices, or flexible plain connectors. As a result, they can provide extensive mounting and wiring options.

Design and Working Principle

The most common design of the terminal block consists of a base plate made by an insulating material with integrated sections with metal contacts in which the wires are connected through screws or other electrical connectors. They have two parts, the header or stationary block and the main body with the contact section. The header is mounted to a junction box, panel or other device and the main body with the contact section is mounted to the base plate and can be easily removed in case of troubleshooting. The contact points are made of various metals with tin- or nickel-plated copper being the most common for industrial uses or are made of stainless steel, brass, copper or pre-tinned wires.

The main advantage of using a screw terminal block is that it provides a neat, reliable and easily identified connection. Furthermore, the electrical isolation provided by the insulating material and contact points makes it possible to protect the wire from electrical dangers like stray currents or short-circuiting. Other advantageous features of screw terminal blocks are their small size, minimizing the possibility of overcrowding, and the possibility of customization. For example, installation can require only a few simple mounting steps, the use of different contact materials, and custom labelling.