surrounded by a metallic shield to protect against interference from
adjacent electrical influence. The shielding on the cable may or may
not be grounded.
Figure 1-2 shows some common symbols for shielded
There are literally hundreds of different
types of electrical and electronic components in use today. However,
three components are widely used in a wide variety of applications.
These three components are found in most circuit schematics of any
complexity. The three components are (a) resistors; (b) capacitors;
and (c) inductors.
Resistors are unquestionably the most commonly
used circuit components.
They are found in almost every electrical
in that they are designed to "resist" the flow of electrical current.
Resistors are typically shown in schematics by the symbol illustrated
in figure 1-3.
In addition to the symbol, the resistor is generally labeled by the
letter "R" followed by a number, e.g., R1, R2, etc. The resistance
value, measured in ohms, may also be indicated. If the resistance is
not indicated, you can determine it by