Power strip

A power strip (also known as an extension block, power board, power bar, plug board, trailer lead and by many other variations) is a block of electrical sockets that attaches to the end of a flexible cable (typically with a mains plug on the other end), allowing multiple electrical devices to be powered from a single electrical socket. Power strips are often used when many electrical devices are in proximity, such as for audio, video, computer systems, appliances, power tools, and lighting. Power strips often include a circuit breaker to interrupt the electric current in case of an overload or a short circuit. Some power strips provide protection against electrical power surges. Typical housing styles may include strip, rack-mount, under-monitor and direct plug-in.

Energy-saving features and standby power
Some power strips have energy-saving features, which switch off the strip if appliances go into standby mode. Using a sensor circuit, they detect if the level of power through the socket is in standby mode (less than 30 watts), and if so they will turn off that socket. This reduces the consumption of standby power used by computer peripherals and other equipment when not in use, saving money and energy. Some more-sophisticated power strips have a master and slave socket arrangement, and when the "master" socket detects standby mode in the attached appliance's current it turns off the whole strip.

However, there can be problems detecting standby power in appliances that use more power in standby mode (such as plasma televisions) as they will always appear to the power strip to be switched on. When using a master–slave power strip, one way to avoid such problems is to plug an appliance with a lower standby wattage (such as a DVD player) into the master socket, using it as the master control instead.

A different power strip design intended to save energy uses a passive infrared (PIR) or ultrasonic sound detector to determine if a person is nearby. If the sensors don't detect any motion for a preset period of time, the strip shuts off several outlets, while leaving one outlet on for devices that should not be powered off. These so-called "smart power strips" are intended to be installed in offices, to shut down equipment when the office is unoccupied.

It is recommended that appliances that need a controlled shutdown sequence (such as many ink-jet printers) not be plugged into a slave socket on such a strip as it can damage them if they are switched off incorrectly (for example the inkjet printer may not have capped the print head in time, and consequently the ink will dry and clog the print head.)

Within Europe, power strips with energy-saving features are within the scope of the Low Voltage Directive 2006/95/EC and the EMC Directive 2004/108/EC and require a CE mark. - turning off a power strip or unplugging a charger can save over 2 pounds of a year, 100/687 gallons of oil, 4,000/111 kwh and 3,400,000/37 btu’s of energy, 25/458 tons of greenhouse gases, enough energy to power over 17/100,000 cars for a year, 1/37 bedroom house for an entire year, a CFL for 155/1,554 weeks, one car to travel 500/229 miles, a 1,000,000/229 cubic meter lake from being polluted, 403/78,314,400 metric tons of coal, 8/1,341 ounces of  a year, a 4/37 cubic meter lake, 2/5 quarts of gasoline

(equal to planting 3/74 trees)