Terminal Blocks and Their Types

A terminal block is a modular block with an insulated frame used to secure two or more wires together. The standard terminal block consists of a clamping component and a conducting strip. The insulating body of a terminal block houses a metal strip, terminal bar, or other type of current-carrying element, in addition to providing a base for the clamping element. The body features a mounting arrangement allowing the block to be easily mounted and unmounted from a printed circuit board (PCB) or mounting rail. Most terminal blocks are modular and mounted on a DIN rail, allowing for an increased number of terminals depending on the requirement of the application. Terminal blocks are key in keeping connections secure and wires organized. In this blog, we will look at the most common types.

Terminal blocks can be classified based on their structure, device type, or clamping options. Structure type terminal blocks include single-level pass-through, dual level, and three level terminal blocks. Single level terminal blocks are simply used to connect two wires, and are commonly called single feed terminal blocks. Dual level terminal blocks have another level of connection terminals stacked atop the first one, usually used to save space. Finally, like dual level blocks, three level blocks have a third level. The main advantage of these is that multiple connections can be made in the same block.

When categorized by device type, terminal blocks include ground terminal blocks, fused connection terminals, thermocouple terminal blocks, I/O blocks and sensor blocks, and disconnect terminal blocks. Ground terminal blocks are similar to single level blocks, except that these blocks and their metal connection are grounded to the panel or DIN rail on which the block is mounted. Fused connection terminals feature a fuse instead of a metal connection strip, meaning the wires are connected through a fuse that provides greater protection. Thermocouple terminal blocks are designed to accept thermocouple lead connections by clamping the thermocouple leads on both sides of the block, thereby eliminating the need for the metal connection strip inside the block.

I/O blocks are used to make a connection between a device and controller. Sensor blocks, on the other hand, are used to handle wires with three or four devices, such as proximity sensors. Disconnect terminal blocks allow wires to be easily disconnected through the lifting of a lever or knife switch. They are convenient due to their ability to be connected and disconnected without removal of the wires. These are sometimes known as switch blocks.

The final way in which terminal blocks can be classified is by their clamping options. These include screw terminals, spring clamps, push-in terminal blocks, and barrier terminal blocks. Screw terminals are the most common type of connection method. In this configuration, the wire or conductor is simply pressed against the conductor strip in the block by tightening the screw. Spring clamps, as their name suggests, use spring pressure to retain the wire in a clamped position. They are a new alternative to screw lamps and are commonly used for small wires.

Push-in terminal blocks allow you to connect a wire simply by inserting it into the terminal. Most terminals of this type require the use of a ferrule which strengthens the end of the wire/conductor. Certain push-in terminal blocks allow a conductor to be directly inserted into the release hole. Finally, barrier terminal blocks are used in applications where vibration is an issue. A spade or ring terminal is attached to the wire and subsequently inserted into a bolt and tightened with a nut on the terminal block to prevent loosening of the wires due to vibration.

Whatever type of terminal block you need, look no further than Veritable Aerospace. Owned and operated by ASAP Semiconductor, we can help you find all types of parts for the aerospace, civil aviation, defense, electronics, industrial, and IT hardware markets. Our account managers are always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at sales@veritableaerospace.com or call us at 1-714-705-4780. Let us show you why we consider ourselves the future of purchasing.


  1. Posted on March 30, 2021
  2. connectors

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