Low-power resistors have a standard set of values. Color-band codes indicate the resistance value as well as a tolerance. The most common types of resistors are the carbon composition and carbon film resistors.
The color code for the resistor value uses two digits and a multiplier digit, in that order, as shown in Figure D.1. A fourth band designates the tolerance. Standard values for the first two digits are listed in Table D.1.
The resistance of a resistor with the four bands of color may be written as
R = (a × 10 + b)m ± tolerance
where a and b are the values of the first and second bands, respectively, and m is a multiplier. These resistance values are for 2 percent and 5 percent tolerance resistors, as listed in Table D.1. The color code is listed in Table D.2. The multiplier and tolerance color codes are listed in Tables D.3 and D.4, respectively. Consider a resistor with the four bands, yellow, violet, orange, and gold. We write the resistance as