Understand the concept
A 3-way switch is a single-pole double-throw switching device, with a common terminal and two traveler terminals. Two 3-way switches can control one light from two locations.
A 4-way switch is inserted between the two 3-way switches to add an additional control location. Its internal contacts either carry travelers straight through or cross them.
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Practice task
Trace the travelers on a paper schematic and label each common terminal. Use a low-voltage trainer or instructor-supervised, fully de-energized lab for practical demonstration.
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