Power Strips

A power strip (also known as a power board, power bar, gangplug or multibox) is a strip of sockets that attaches to the end of a flex and allows multiple devices to be plugged in. more...

As such it can be considered a type of trailing socket though that term is more often used for single and double cable mounted sockets. The term is also used to refer to the complete assembly with the power strip on one end and a plug on the other. Power strips are often used when many electrical devices are in close proximity, especially with audio/video and computer systems.

Control

Power strips can include a switch to turn all devices on and off. In a few cases they may even have all outlets individually switched. Some very expensive strips exist that can detect one device being turned on (say the PC itself in a computer setup) and turn everything else on. Remote control strips also exist to allow a group of devices to be switched remotely.

Surge Protection and Filtering

Many power strips have built in surge protectors and/or EMI/RFI filters: these are sometimes described as electrical line conditioners. Some also provide surge suppression for phone lines, TV cable coax, or network cable.

Surge suppression is usually provided by one or more metal-oxide varistors (MOVs), which are inexpensive two-terminal semiconductors. They act as very high speed switches, closing at any of several designed voltages. The most commonly used are built to close at a voltage somewhat above the local mains supply. In the US, this is (nominally) 115 VAC. however it should be borne in mind that this voltage is RMS not peak and also that it is only a nominal value.

In most of the developed world, mains electrical circuits are (supposed to be) grounded (earthed), so there will be a live wire, a neutral wire, and a ground wire. Power strips often come with only one MOV mounted between the live and neutral wires. More complete (and desirable) power strips will have three MOVs, mounted between each possible pair of wires. Since MOVs degrade somewhat each time they are triggered, power strips using them have a limited, and unpredictable, protective life.

More elaborate power strips may use inductor-capacitor networks to achieve a similar effect of protecting equipment from high voltage spikes on the mains circuit. Such arrangements are more expensive, but less prone to silent degradation than MOVs.

Indication

Many power strips have a neon light for power indication. Surge protected strips are likely to have more lights to indicate the status of the surge protection system.

Socket arrangement

Socket arrangement varies considerably, but for access reasons there are rarely more than two rows. In the UK units featuring four sockets in a square arrangement are fairly common although these are not strip-shaped and hence not normally referred to as power strips.

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