A power strip is a way to plug multiple devices into a single wall socket. It differs from other outlet-expansion devices in that the sockets in a power strip are in a straight line on one side of a long narrow enclosure attached to the wall socket with an extension cord, instead of being on a faceted cluster, t-shape, or double-sided block hanging from the socket itself.

The main reasons a power strip is a popular method of socket expansion are safety and convenience. Socket clusters are shaped the way they are to reduce the amount of metal used, so all plugs are inserted inward towards a common electrical contact point. This is unsafe for many reasons, from creating a high current density at the point of contact that causes excessive heat, to being difficult to extract plugs from due to their "pincushion" design. A power strip employs two robust power rails that extend along the line of sockets that are able to handle the current load, and the linear design makes inserting and removing plugs much easier.

Since the load on the line feeding the wall socket can still exceed its limit due to the number of items now pulling current from it, a circuit protection device is usually included in the power strip, to provide additional safety. The quality of the device can range from a simple replaceable fuse to a heavy-duty fast-switching resettable circuit breaker. Some power strips are even available with lightning arrestors (not to be confused with circuit breakers.)

A recent development has been to add filters for power and/or signal to the strip. This has become more popular since the expansion of the home office and the home theater, both venues where multiple electronic devices are used and reliability and quality become more than convenience issues. Often additional jacks are provided to plug in phone lines and RF signal cables to allow them to benefit from the protection circuitry.

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