A Guide to Terminal Blocks

A terminal block is a modular block with an insulated frame used to secure two or more wires together. Terminal blocks consist of a clamping component and a conducting strip. The insulated frame of a terminal block houses a current carrying element (either a metal strip or terminal bar) while providing a base for the clamping element. The body also features a mounting arrangement, allowing the block to be easily mounted on or unmounted from a printed circuit board or mounting rail. Most terminal blocks are modular and mounted on DIN rails, allowing the number of terminals to be increased.

There are many different types of terminal blocks, classified primarily based on their structure and device type.

Structure Type

  • Single level pass-through terminal blocks: Terminal blocks of this type are used to connect wires together in wire-to-wire connection. These are also called single feed terminal blocks and are one of the most simple types of terminal blocks.

  • Dual level terminal blocks: These terminal blocks offer another level of connection terminals stacked atop the first one. This is helpful in saving space for large configurations.

  • Three level terminal blocks: These are like dual level blocks but feature an additional level. An advantage of multilevel blocks is that many connections can be made in a single block.

Device Type

  • Ground terminal blocks: Ground terminal blocks look similar to single level pass-through terminals, but these blocks, and the metal connection where the wire is terminated, is connected to the panel or DIN rail on which the block is mounted.

  • Fused connection terminals: These are also similar to pass-through blocks, but the metal connection strip is replaced with a fuse. The wires being connected through a fuse provides added protection.

  • Thermocouple terminal blocks: Terminal blocks of this type are designed to accept thermocouple lead connections. Certain types of thermocouple connectors clamp the thermocouple leads together on both sides of the block, therefore eliminating the metal connection strip within the block. Despite this, some thermocouple blocks a metal connection strip of the same metal as the wire.

  • I/O blocks and sensor blocks: I/O blocks are used to create a connection between a device and a controller. Sensor blocks are capable of handling three or four wire devices such as proximity sensors.

  • Disconnect terminal blocks: These blocks allow for disconnection simply by lifting a lever or switch. They are also known as switch blocks and are widely used in applications that require regular connection and disconnection without the removal of wires.

  • Power distribution blocks: These blocks are used specifically for electrical power distribution. They serve as a convenient, economical, and safe way to distribute power from a single input source to multiple outputs. In a normal configuration, a single wire is connected to the input terminal and multiple output terminals are provided as the output. This allows wires to be neat, organized, and accessible.

Terminal blocks provide an ideal solution for complex electrical system connections. For all types of terminal blocks and much more, look no further than NSN Unlimited. We are a premier supplier of all types of aviation parts as well as NSN parts, electronics parts, and much more for various military and civilian applications. Owned and operated by ASAP Semiconductor, we can help you find all types of unique parts for the aerospace, civil aviation, and defense industries. Our dedicated account managers are standing by 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@nsnunlimited.com or call us at +1(714)-705-4780.


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