3-8
The number of poles in a switch is independent of the number of throws and whether it is a single or
double break switch. The number of throws in a switch is independent of the number of poles and
whether it is a single or double break switch. In other words, each characteristic of a switch (poles,
throws, break) is not determined by either of the other characteristics. Figure 3-6 shows the schematic
symbols for several different switch configurations.
Figure 3-6.—Schematic symbols of switch configurations.
Rotary Switches
A rotary switch is a midcontact switch part of the schematic with the contacts arranged in a full or
partial circle. Instead of a pushbutton or toggle, the mechanism used to select the contact moves in a
circular motion and must be turned. Rotary switches can be manual or automatic switches. An automobile
distributor, the ignition switch on a motor vehicle, and the channel selector on some television sets are
rotary switches.
The automobile distributor cap and rotor are an example of the simplest form of an automatic rotary
switch. Figure 3-7 shows a portion of an automobile ignition system with the distributor cap and rotor
shown. The rotor is the portion of this switch that moves (rotates) and selects the circuit (spark plug). The
rotor does not actually touch the contacts going to the spark plugs, but the signal (spark) jumps the gap
between the rotor and the contacts. This switch has one input (the rotor) and six positions (one for each
spark plug). The schematic diagram for this rotary switch is shown below the illustration of the distributor
cap.
