Figure 2-1.--Knife switches.

(3PDT): 4-pole, single-throw (4PST); and 4-pole,

Knife Switches

double-throw (4PDT). The voltage ratings range from

Knife switches are basic power switches from

20 volts to 600 volts, and the amperage ratings range

which most modern switches have been developed. A

from 1 ampere to 30 amperes.

single-pole, single-throw (SPST) knife switch

consists of a single copper blade hinged at one end and

Push-Button Switches

designed to fit tightly between two copper jaws, or

clips, at the other end. An insulated handle is fastened

The normal contact arrangement of a push-button

to the copper blade to open and close the switch.

switch is either make or break, as shown by the

Terminals are provided for connecting the leads.

schematic symbols in figure 2-3, view A. View B of

figure 2-3 is a picture of a push-button switch. The

A double-pole, single-throw (DPST) knife switch

(fig. 2-1, view A) has two blades with one set of clips

for each blade and an insulated handle that operates

both blades simultaneously. Double-throw switches

(fig. 2-1, view B) have two sets of clips (one set at each

end) so the blades can be thrown into either set of clips

to shift from one circuit to another.

Toggle Switches

Representative examples of toggle switches are

shown in figure 2-2, with the schematic symbols

shown beneath each switch. View A of figure 2-2

shows a SPST toggle switch, rated at 20 volts and 20

amperes, and having two solder terminals. This type

of switch opens and closes electric circuits.

View B of figure 2-2 shows a single-pole,

double-throw (SPDT) switch, rated at 250 volts and 1

ampere, and having three screw terminals. One use of

this switch is to turn a circuit on at one place and off

at another place. It is sometimes called a 2-way switch.

View C of figure 2-2 shows a DPST switch, rated

at 250 volts and 1 ampere, and having four solder

terminals.

View D of figure 2-2 shows a double-pole,

Figure 2-2.--Toggle switches.

double-throw (DPDT) switch, rated at 125 volts and 3

amperes, and having six solder terminals.

The following types of switches are also used:

3-pole, single-throw (3PST); 3-pole, double throw

Figure 2-3.--Push-button switch.

Figure 2-1.--Knife switches.

2-2