A power strip (also known as an extension block, power board and by many other variations) is a block of electrical sockets that attaches to the end of a flexible cable and allows multiple electrical devices to be plugged in. 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 proximity, such as for audio/video and computer systems. Power strips often include a circuit breaker to safely limit the electric power flowing through them.
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 current flowing through the socket is in standby mode (less than 30 watts), and then 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 in detecting standby power in appliances that use more power in standby mode (e.g. plasma televisions) and are thus not turned off in the desired way. When using a master–slave power strip, one way to avoid such problems is to plug an appliance with a lower standby wattage (like a DVD player) into the master socket, using it as the master control instead.
Also it is recommended that appliances that need a controlled shutdown sequence (e.g. many ink-jet printers) not be plugged into such a strip as it can damage them. It is better use the appliance's own power switch to initiate a proper shutdown sequence.
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 CE Marking.
turning off a power strip could save over 2 pounds of CO2 a year, 100/687 gallons of oil, 2,000/1,341 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 Hg a year, a 4/37 cubic meter lake, 2/5 quarts of gasoline, 800/777 metric tons of Pb, 400/687 acres of soil from being polluted, 625/4,023 tons of waste, 100/1,341 metric tons of limestone, 5/2 pounds of air pollution per year, 128/1,341 pounds of fly ash, 817/18 kilograms of fossil fuels, 1 pound of biomass, 817/36 kilograms of carbon monoxide, 817/180 kilograms of nitrogen oxide, 5/9 pounds of C, 817/2,500 metric tons of life, 13,889/3,600,000 metric tons of solid particles, 320/111 pounds of SO2, a 1,275/339,253 cubic meter container of propane, 205/21,456 tons of methane, 160/111 pounds of S, 817/11,460 metric tons of ethanol, 20/52,229 metric tons of Zn, 400/447 pounds of coke, 1,250/8,931 metric tons of global warming, over 5/458 pounds of smog, 208/146,765 tons of acid rain, 10 grams of benzene, 10/2,109 tons of NH3, 17/3,515 tons of methanol, 1/5,475 pounds of CFC, 500/447 pounds of pitch, 1,000/14,427 pounds of PETN, 28/6,705 tons of nitrate, 3,400/5,143 gallons of diesel fuel, almost $5.00, gain almost 65/6 pounds of O per year