Alberto: There's no rules, but it works sorta like this:

RESISTORS Usually marked in ohms using a standard code: First two numbers is the value Third number is the multiplier 102 = 1.0 x 10� ohm = 1000 ohm = 1 kW CAPACITOR Usually not marked. When marked, 1. Some capacitors follow the same notation as resistors, using the last number in the sequence to denote the number of zeros to add and hence you can work out the correct number of Farads. 2. Some capacitors are marked with a code, consisting of one or two letters and a digit. The first letter, if present, is a code for the manufacturer (i.e., K for Kemet, etc.), the second letter the mantissa, and the digit the exponent (multiplier) of the capacitance in pF. So, S3 = 4.7 x 10� pf = 4.7nF from an unknown manufacturer KA2 = 1.0 x 10� pF = 100 pF from Kemet. Letter Mantissa Letter Mantissa Letter Mantissa Letter Mantissa A 1.0 J 2.2 S 4.7 a 2.5 B 1.1 K 2.4 T 5.1 b 3.5 C 1.2 L 2.7 U 5.6 d 4.0 D 1.3 M 3.0 V 6.2 e 4.5 E 1.5 N 3.3 W 6.8 f 5.0 F 1.6 P 3.6 X 7.5 m 6.0 G 1.8 Q 3.9 Y 8.2 n 7.0 H 2.0 R 4.3 Z 9.1 t 8.0 y 9.0

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