have a specific letter code assigned to it, then it may be defined by the style sheet number listed in IEC TR 60083. Not all plugs are included in the letter system; for example, there is no designation for the plugs defined by the Thai National Standard TIS 116-2549, though some web sites refer to the three-pin plug described in that standard as "Type O". Identification guide Table of mains voltages, frequencies, and plugs See also Delta-wye transformer Electrical wiring Electric power transmission Electrification Electrical grid List of railway electrification systems Mains electricity References External links Electricity Electric power Mains Electrical standards Electrical wiring Elect Mains power connectors fi:Verkkovirta ur:مینز برق بلحاظ ملک