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The electronic color code is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables. The electronic color code was developed in the early 1920s by the Radio Manufacturers Association (now part of Electronic Industries Alliance〔(EIA )〕 (EIA)), and was published as EIA-RS-279. The current international standard is IEC 60062.〔(IEC 60062:2004 ) Title: "Marking codes for resistors and capacitors" (IEC Webstore)〕 published by International Electrotechnical Commission. Colorbands were used because they were easily and cheaply printed on tiny components. However, there were drawbacks, especially for color blind people. Overheating of a component or dirt accumulation, may make it impossible to distinguish brown from red or orange. Advances in printing technology have now made printed numbers practical on small components. Where passive components come in surface mount packages, their values are identified with printed alphanumeric codes instead of a color code. ==Resistor color-coding== To distinguish left from right there is a gap between the C and D bands. * band A is the first significant figure of component value (left side) * band B is the second significant figure (some precision resistors have a third significant figure, and thus five bands). * band C is the decimal multiplier * band D if present, indicates tolerance of value in percent (no band means 20%) For example, a resistor with bands of ''(yellow, violet, red, and gold )'' has first digit 4 (yellow in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms. Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199 for further details. Tight tolerance resistors may have three bands for significant figures rather than two, or an additional band indicating temperature coefficient, in units of ppm/K. All coded components have at least two value bands and a multiplier; other bands are optional. The standard color code per EN 60062:2005 is as follows: Resistors use preferred numbers for their specific values, which are determined by their tolerance. These values repeat for every decade of magnitude: 6.8, 68, 680, and so forth. In the E24 series the values are related by the 24th root of 10, while E12 series are related by the 12th root of 10, and E6 series by the 6th root of 10. The tolerance of device values is arranged so that every value corresponds to a preferred number, within the required tolerance. Zero ohm resistors are made as lengths of wire wrapped in a resistor-shaped body which can be substituted for another resistor value in automatic insertion equipment. They are marked with a single black band.〔(NIC Components Corp. NZO series zero-ohm resistors. )〕 The 'body-end-dot' or 'body-tip-spot' system was used for radial-lead (and other cylindrical) composition resistors sometimes still found in very old equipment; the first band was given by the body color, the second band by the color of the end of the resistor, and the multiplier by a dot or band around the middle of the resistor. The other end of the resistor was colored gold or silver to give the tolerance, otherwise it was 20%.〔''Reference Data for Radio Engineers'', Federal Telephone and Radio Corporation, 2nd edition, 1946 page 52〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Electronic color code」の詳細全文を読む スポンサード リンク
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