A two-way light switch requires a three-way cable (three wires plus ground – four conductors in total) to pass light from any station. This means that, at any time, any of the switches can be flipped over so that it is turned on in the lower position or turned off in the upper position. The wall wiring must be rewired if there is only one two-way cable. Adding another cable to the existing installation will not be as easy as pulling the correct cable to replace the old one.
The third cable offers the possibility to pass through both ends of the cable. The switches used in each position must be two-way switches, which allow you to choose between two different directions for electric current. This is the wiring behind the lighting circuits that saves time, such as the light switch in the kitchen which turns off the light in the garage, and the same circuit can be turned off in the front of the garage, avoiding having to go back to The kitchen . Another application could be the staircase light on different floors, avoiding having to go up or down to get the switch.
How Do Two Way Light Switches Work?
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Two of the three cables carry power to each end of the installation. The third provides redundant switching on both ends. The ground wire is common to the entire installation and must not be used for purposes other than grounding on both ends. Color coding is essential. The red wire is the “traveler” wire and it is the one that carries the current switched from one switch to another. The two black wires are the “hot” wires that have power connected to the circuit and the green wire is the earth connection between all the devices.