Krone block termination is a type of electrical connection often used in telephony. It is named because the solid copper wires are open-ended slots which are a type of 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 krone block tool is used to push the wire down firmly and properly into the slot. Some will automatically cut any excess wire off The exact size and shape of the tool blade varies by manufacturer, which can cause problems for those working on existing installations, especially when there is a poorly-documented mix of different brands.
Krone block terminations are a very quick and easy way to connect wiring, as there is no stripping of insulation and no screws to loosen and tighten. Those
products 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.
Marginal practices like these are strongly discouraged in large or mission-critical installations, because they can introduce extremely troublesome intermittent connections, as well as more-obvious outright bad connections. Once the contact blades in a Krone block termination are "sprung apart" by poor practices, the entire block often must be replaced to restore reliable connections.
In addition, Krone block terminations are being used to handle larger numbers of faster data signals, requiring greater care and proper procedures to control impedance and crosstalk.