Chargers and power adapters symbols
Markings on chargers, power adapters, transformers and battery packs: insulation class, AC and DC, plug polarity, indoor use, transformer type, fuses and efficiency level.
BatteryChargers and power adaptersBatteryUsed on battery-powered equipment to mark battery-related parts, for example the cover of the battery compartment or the connection terminals for the battery.On IEC 60417
Battery orientation (+ / -)Chargers and power adaptersBattery orientation (+ / -)Marks the battery holder and shows how the cells must sit in it: the end with the stub and the plus sign is positive. Insert batteries so their + and - ends match the marking; check the polarity each time you change them.On IEC 60417
Class II equipment (double insulation)Chargers and power adaptersClass II equipment (double insulation)The device or power adapter is built to protection class II: its live parts are separated from everything you can touch by double or reinforced insulation, so its safety does not rely on a protective earth and it has no earth connection. An insulating plastic housing can make up part or all of that extra insulation. A two-pin plug without an earth contact is therefore normal for these products.On IEC 60417
Class III constructionChargers and power adaptersClass III constructionMarks a transformer or appliance built to protection class III, as classified in the transformer safety standard EN 61558-1. It is one of the three construction-class marks printed on transformers and power supplies, next to class I (earth symbol in a circle, needs a protective earth) and class II (double square, double insulation).On EN 61558
DC plug polarity: centre positiveChargers and power adaptersDC plug polarity: centre positiveShows the polarity of a round (barrel) DC plug or socket. The dot stands for the centre pin and the C around it for the outer sleeve; the sign joined to each part gives its polarity. Here the dot is joined to plus and the C to minus, so the centre pin is positive and the sleeve negative. When using a replacement or universal adapter, make sure its polarity symbol matches the one on the device as well as the voltage.On IEC 60417
Detachable power supply unitChargers and power adaptersDetachable power supply unitShows that the device's battery or battery pack is charged through a separate, detachable power supply unit supplied with it. Charge it only with the supplied adapter or charging station.On Chargers and power adapters
Direct current (DC)Chargers and power adaptersDirect current (DC)Shows that a voltage, current or connection is direct current. On chargers, adapters and devices it usually sits next to the DC side: the adapter output and the device's DC input socket (for example 15 V with this symbol and 1.5 A), or a USB port's supply (5 V, 1 A). The mains side is marked with the wave (~) for alternating current instead.On IEC 60417
Efficiency level VIChargers and power adaptersEfficiency level VIAn efficiency grade for external and internal power supplies. Efficiency levels are a standard way of grading how efficiently power supplies work, counted in Roman numerals up to level VI, the most efficient. An adapter marked VI meets the highest of these levels.On Chargers and power adapters
For indoor use onlyChargers and power adaptersFor indoor use onlyThe power adapter or device is made only for use indoors. Use it in dry rooms and keep it away from rain, splashes and damp places; moisture getting inside can cause a short circuit or an electric shock.On IEC 60417
FuseChargers and power adaptersFuseMarks a fuse, for example on a transformer, power supply or device rating plate. The fuse cuts the circuit when too much current flows.On EN 61558
Non-short-circuit-proof safety isolating transformerChargers and power adaptersNon-short-circuit-proof safety isolating transformerMarks a safety isolating transformer that is not short-circuit-proof on its own. The two short legs under the circles distinguish it from the short-circuit-proof version, which has a small closed box there. Such a transformer depends on separate protection against overload or a short circuit on its output.On EN 61558
Safety isolating transformerChargers and power adaptersSafety isolating transformerThe two overlapping circles stand for the transformer's two windings and the shield for safety isolation: the unit is a safety isolating transformer, listed under EN 60742, with its variants under EN 61558-2-6. Its low-voltage output winding is separated from the mains input by safety insulation. Variants add a small box underneath (short-circuit-proof), two short legs (not short-circuit-proof) or a letter F (self-protecting).On EN 61558
Self-protecting (fail-safe) safety isolating transformerChargers and power adaptersSelf-protecting (fail-safe) safety isolating transformerThe letter F next to the safety isolating transformer shield marks a self-protecting (fail-safe) safety isolating transformer under the EN 61558 series. Without the F the shield is a plain safety isolating transformer; a small box under the circles instead means short-circuit-proof.On EN 61558
Short-circuit-proof safety isolating transformerChargers and power adaptersShort-circuit-proof safety isolating transformerMarks a short-circuit-proof safety isolating transformer, as found in plug-in power adapters. If the output is overloaded or short-circuited, its temperature stays within the set limits, and once the overload or short circuit is removed it still meets all the safety requirements of its standard. The small box under the circles is what distinguishes it from the plain safety isolating transformer mark.On EN 61558
Switch-mode power supplyChargers and power adaptersSwitch-mode power supplyMarks a power adapter that is an electronic switch-mode power supply (SMPS), as opposed to a conventional transformer. It describes how the adapter is built; it does not ask you to do anything.On Chargers and power adapters
Thermal cut-outChargers and power adaptersThermal cut-outMarks a thermal cut-out: a temperature-operated protective device in the transformer or power supply that breaks the circuit when it gets too hot. The Greek letter theta above the fuse-like rectangle stands for temperature.On Chargers and power adapters