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An electronic color code is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables. Different codes are used for wire leads on devices such as transformers or in building wiring.

Before industry standards were established, each manufacturer used their own unique system for color coding or marking their components. In the 1920s, citation needed the RMA resistor color code was developed by the Radio Manufacturers Association (RMA) as a fixed resistor coloring code marking. In 1930, the first radios with RMA color coded resistors were built. Over many decades, as the organization name changed (RMA, RTMA, RETMA, EIA) so was the name of the code. Though known most recently as EIA color code , the four name variations are found in books, magazines, catalogs, and other documents over more than 90 years. In 1952, it was standardized in IEC 62:1952 by the International Electrotechnical Commission (IEC) and since 1963 also published as EIA RS-279 . Originally only meant to be used for fixed resistors, the color code was extended to also cover capacitors with IEC 62:1968. The code was adopted by many national standards like DIN 40825 (1973), BS 1852 (1974) and IS 8186...

Color band system edit To distinguish left from right there is a gap between the C and D bands: In the above example, a resistor with bands of red, violet, green, and gold has first digit 2 (red; see table below), second digit 7 (violet), followed by 5 (green) zeroes: 2 700 000  ohms . Gold signifies that the tolerance is ±5%. Precision resistors may be marked with a five band system, to include three significant digits, a power of 10 multiplier, and a tolerance band. An extra-wide first band indicates a wire-wound resistor. 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 IEC 60062:2...

Capacitors may be marked with 4 or more colored bands or dots. The colors encode the first and second most significant digits of the value in picofarads, and the third color the decimal multiplier. Additional bands have meanings which may vary from one type to another. Low-tolerance capacitors may begin with the first 3 (rather than 2) digits of the value. It is usually, but not always, possible to work out what scheme is used by the particular colors used. Cylindrical capacitors marked with bands may look like resistors. Color Significant digits Multiplier Tolerance % Characteristic DC working voltage V Operating temperature °C EIA/vibration Hz   Black 0 1 — — — −55 to +70 10 to 55 Brown 1 10 ±1 B 100 — — Red 2 100 ±2 C — −55 to +85 — Orange 3 1 000 — D 300 — — Yellow 4 10 000 — E — −55 to +125 10 to 2000 Green 5 100 000 ±0.5 F 500 — — Blue 6 1 000 000 — — — −55 to +150 — Violet 7 10 000 000 —...

Standards IEC 60062 / EN 60062 do not define a color code for inductors, but manufacturers of small inductors use the resistor color code, typically encoding inductance in microhenries. A white tolerance ring may weasel words indicate custom specifications.

The part number for small JEDEC "1N"-coded diodes—in the form "1N4148"—is sometimes encoded as three or four rings in the standard color code, omitting the "1N" prefix. The 1N4148 would then be coded as yellow (4), brown (1), yellow (4), grey (8).

Transformer edit Power transformers used in North American vacuum-tube equipment were often color-coded to identify the leads. Black was the primary connection, red secondary for the B+ (plate voltage), red with a yellow tracer was the center tap for the B+ full-wave rectifier winding, green or brown was the heater voltage for all tubes, yellow was the filament voltage for the rectifier tube (often a different voltage than other tube heaters). Two wires of each color were provided for each circuit, and phasing was not identified by the color code. Audio transformers for vacuum tube equipment were coded blue for the finishing lead of the primary, red for the B+ lead of the primary, brown for a primary center tap, green for the finishing lead of the secondary, black for grid lead of the secondary, and yellow for a tapped secondary. Each lead had a different color since relative polarity or phase was more important for these transformers. Intermediate-frequency tuned transformers were cod...