This is a typical (right!) picture out of a "Do-It-Yourself" book:
3-WAY-SWITCH = "How to wire a lamp fixture with 2 independent switches"
It explains "How-To-Do" B U T N O T "How-To-Know" !
My 24 years of experience in USA neigborhoods as the
"Helping Hand of Our German Engineer" tought me,
that this task seems to be a "Master's Job" ...
Typical Situations found:
-------------------------
(a) When SWITCH-ONE=ON, SWITCH-TWO can switch LAMP=ON/OFF
(b) When SWITCH-ONE=OFF, LAMP=OFF, when SWITCH-TWO=ON/OFF = always!
WRONG !!!
The LAMP should be switched ON/OFF independent from the position of the
OTHER SWITCH !!! It happens, because N O K N O W L E D G E behind!
(1st) You have to know how the SWITCH is wired inside
and (2nd) You have to know the WIRE-DIAGRAM ...
Observe the (!) "Wire-Crossing" - It has an advantage:
LAMP = OFF, when BOTH SWITCHES are DOWN ( or UP ),
LAMP = ON, when ONE SWITCH is UP.
When you have understood the diagram, than it is easy to extend.
If you would like to have a third switch to control the light:
Add a "4-WAY-SWITCH" in the DIAGRAM's (!) "Wire-Crossing" area ...
4-WAY-SWITCH in DOWN- & in its UP-Position
... LAMP = OFF, when ALL SWITCHES are DOWN
R E M A R K S : The naming "2-WAY", "3-WAY", "4-WAY" is misleading:
+------------------------------------------------------------------------+
| With "2-WAY"-Wiring you have 1 way to switch the light on/off; |
| with "3-WAY"-Wiring you have 2 ways to switch the light on/off; |
| with "4-WAY"-Wiring you have 3 ways to switch the light on/off. |
| |
| OR: " WITH 3-WAY-WIRING YOU CAN MAKE AT LEAST 3 M I S T A K E S " |
+------------------------------------------------------------------------+
Much more appropriate would be "2-WIRE"-, "3-WIRE"-, "4-WIRE"- SWITCHES
impressum:
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© C.HAMANN http://public.BHT-Berlin.de/hamann 05/27/21
