Electronic color code
Before industry standards were established, each manufacturer used its own unique system for color coding or marking their components.
Though known most recently as EIA color code, the four name variations are found in books, magazines, catalogs, and other documents over more than 95 years.
[4] Originally only meant to be used for fixed resistors, the color code was extended to also cover capacitors with IEC 62:1968.
Overheating of a component or dirt accumulation may make it impossible to distinguish brown from red or orange.
[6] Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199[7] for further details.
The standard color code per IEC 60062:2016 is as follows: Resistors use various E series of preferred numbers for their specific values, which are determined by their tolerance.
Zero ohm resistors, marked with a single black band,[10] are lengths of wire wrapped in a resistor-like body which can be mounted on a printed-circuit board (PCB) by automatic component-insertion equipment.
They are typically used on PCBs as insulating "bridges" where two tracks would otherwise cross, or as soldered-in jumper wires for setting configurations.
The same resistance is encoded by: Useful mnemonics have been created to make it easier to remember the numeric order of resistor color bands: The following example includes the tolerance codes — gold, silver and none: The colors are sorted in ascending order of frequency to make them easy to remember and to reduce the significance of possible read errors due to color shifts and fading over time: red (2), orange (3), yellow (4), green (5), blue (6), violet (7).
Extra bands on ceramic capacitors identify the voltage rating class and temperature coefficient characteristics.
Polyester film and "gum drop" tantalum electrolytic capacitors may also be color-coded to give the value, working voltage and tolerance.
A three-dot EIA code was used for 500 volt 20% tolerance capacitors, and the dots signified first and second significant digits and the multiplier.
[18] 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.
Intermediate-frequency tuned transformers were coded blue and red for the primary and green and black for the secondary.
Mains electrical wiring, both in a building and on equipment, was once usually red for live, black for neutral, and green for earth, but this was changed as it was a hazard for color-blind people, who might confuse red and green; different countries use different conventions.
