Please select from
the list below or the links on the right.
How to use
The most common switching circuits
Use a switch to turn On and
Off one light bulb
Use two switches to turn On
and Off one light bulb
Use three or more switches to
turn On and Off one light bulb
Use one switch to alternate
Off On two light bulbs
The following diagrams show how
switches are used for the above four switching circuits.
|Simple Electric Circuit
A simple electric circuit usually consists
of one power source (such as a battery), one load (such as a light
bulb), one switch and wires connecting them in a closed loop in series.
Using SPDT or 3-way switches
|Three-way switches control lights and
receptacles from two points: for example, a light in a hallway that can
be operated from the first floor and second floor. The diagram in the
right is a simple representation
of a light bulb circuit that can be controlled
via two switches.
|Switch among the Light Bulbs
You can use SPDT switches to alternate
lighting up two different light bulbs. This method is used for some
OPEN/CLOSE signs and some manual controlled Red/Green traffic lights.
The two light bulbs in this circuit can never be ON at the same time.
Using DPDT Switches
Control One Light Bulb With Three Switches
If you are want to control one light bulb with
3 or more switches, you will need two SPDT switches and some DPDT switches in
In the DPDT above when the connection are
straight (Z-X and Y-W) or crossed (Z-W and Y-X). In some DPDT switches you will
need to make your own cross connection by connecting the throws in a cross form.
How 4-way switches work -- an animation
Shown above is an animation of a circuit using
three switches to control a light. The center switch is 4-way switch (DPDT),
while the outer two switches are 3-way (SPST).
Note that in the above animation, the wires are
color coded to indicate their voltage state, rather than the standard NEC
Glossary of Switches:
SPST: Single Pole Single Throw
SPDT: Single Pole Double Throw (Three way
DPST: Double Pole Single Throw
DPDT: Double Pole Double Throw (four way
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