Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search

Figure 3-10. - Switch schematic symbols.

32NE0295.GIF (3682 bytes)


You have learned that switches are classified by the number of poles, throws, and breaks. There are other factors used to describe a switch such as the type of actuator and the number of positions. In addition, switches are classified by whether the switch has momentary contacts or is locked into or out of position and whether or not the switch is snap-acting.

Type of Actuator

In addition to the pushbutton, toggle, and knife actuated switches already described, switches can have other actuators. There are rocker switches, paddle switches, keyboard switches and mercury switches (in which a small amount of mercury makes the electrical contact between two conductors).

Number of Positions

Switches are also classified by the number of positions of the actuating device. Figure 3-11 shows three toggle switches, the toggle positions, and schematic diagrams of the switch. Figure 3-11(A) is a single-pole, single-throw, two-position switch. The switch is marked to indicate the ON position (when the switch is closed) and the OFF position (when the switch is open). Figure 3-11(B) is a single-pole, double-throw, three-position switch. The switch markings show two ON positions and an OFF position. When this switch is OFF, no connection is made between any of the terminals. In either of the ON positions, the center terminal is connected to one of the outside terminals. (The outside terminals are not connected together in any position of the switch.) Figure 3-11(C) is a single-pole, double-throw, two-position switch. There is no OFF position. In either position of this switch, the center terminal is connected to one of the outside terminals.

Figure 3-11. - Two- and three-position switches.

32NE0296.GIF (9921 bytes)

Momentary and Locked Position Switches

In some switches, one or more of the switch positions are MOMENTARY.

This means that the switch will only remain in the momentary position as long as the actuator is held in that position. As soon as you let go of the actuator, the switch will return to a non-momentary position. The starter switch on an automobile is an example of a momentary switch. As soon as you release the switch, it no longer applies power to the starter.

Another type of switch can be LOCKED IN or OUT of some of the switch positions. This locking prevents the accidental movement of the switch. If a switch has locked-in positions, the switch cannot be moved from those positions accidentally (by the switch being bumped or mistaken for an unlocked switch).

Western Governors University

Privacy Statement - Copyright Information. - Contact Us

Order this information in Print

Order this information on CD-ROM

Download in PDF Format


Click here to make your Home Page

Page Title: Switch schematic symbols.
 | Up | Updates




Information Categories
.... Administration
Food and Cooking
Nuclear Fundamentals
  Educational CD-ROM's
Printed Manuals
Downloadable Books


Back ] Home ] Up ] Next ]

Back ] Home ] Up ] Next ]

Order this information in Adobe PDF Printable Format

Privacy Statement - Press Release - Copyright Information. - Contact Us -

Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business