Break out box

A breakout box is a critical piece of electrical test equipment used to support integration testing, expedite maintenance, and streamline the troubleshooting process at the system, subsystem, and component level by simplifying the access to test signals. Breakout boxes span a wide spectrum of functionality: (i) some serve to break out every signal connection coming into a unit while others breakout only specific signals commonly monitored for either testing or troubleshooting purposes; and some are used on electrical connectors and others are used on optical fiber connectors.

A breakout box serves as a troubleshooting tool to determine the wiring of an electrical connector interface on a networking device or computer. Typically, a breakout box is inserted between two electrical devices to determine which signal or power interconnects are active. Breakout boxes are extremely useful in troubleshooting connection problems resulting from manufacturing errors (e.g., miswiring) or defective interconnects resulting from broken wiring. Breakout boxes are specific examples of a more general category of network testing equipment called "status monitors".

A variety of these monitoring devices are available for testing serial interfaces, including RS-232, RS-449, V.35, and X.21, as well as specialty interfaces. They generally come with a variety of connectors and are quick and easy to use for isolating problems with serial transmission connections in networking, telecommunications, and industrial settings.

The term breakout box is derived from the mechanical enclosure in which a connector's aggregate connections are separated (i.e., broken out) into individual signal or current carrying wires or cables. Often, if there are only a few connections, then a breakout cable (also called an octopus cable) may be used, as is common on notebook computers.

The most common breakout boxes use D-subminiature connectors (sometimes referred to as D-sub connectors and sometimes erroneously as DB connectors) and are configured with both male and female DE-9, DA-15, DB-25, DC-37 or DD-50 standard density connectors and related test points. These units can also be used to simulate special cables, interconnect RS-232 devices, or adapt test equipment to an RS-232 device.

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