Punch Down Tools

A punch block (also punchblock, punchdown block, quick-connect block and other variations) is a type of electrical connection often used in telephony. more...

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It is named because the solid copper wires are punched down into short open-ended slots known as Insulation-displacement connectors. These slots, usually cut crosswise (not lengthwise) across an insulating plastic bar, contain two sharp metal blades which cut through the wire's insulation as it is punched down. These blades hold the wire in position and make the electrical contact with the wire as well.

A tool called a punch tool or punchdown tool is used to push the wire down firmly and properly into the slot. Some will automatically cut any excess wire off. (Note that in crafts, a "punch tool" means a hole puncher, often for things other than paper.)

Punch blocks are a very quick and easy way to connect wiring, as there is no stripping of insulation and no screws to loosen and tighten. Punch blocks are often used as patch panels, or as breakout boxes for PBX or other similar key phone systems with a 50-pin RJ-21 (Amphenol) connector. They are sometimes used in other audio applications, such as in reconfigurable patch panels.

Examples

A 66_block (or "M Block") is used in telephone systems;

Read more at Wikipedia.org