4 way switches have two traveler terminals the traveler must be wired. Due to creative minds and new wiring techniques we now know that there are several methods to wire two 3 way switches ans still accomplish the same result.
Remote On Off 3 Way Light Switch Kit Manualzz
Why is it called a 3 way switch. Bill the original title. Now lets look at the feature specific differences. Both switches on both switches off or one switch on and one switch off. For example a long hallway or stairway might use a pair of three way switches at each end so that lights can be turned on when approaching one end of the hall or stairway then shut off from the other end. In 3 way switches you use two control a single appliance from two different locations. The three way switch is a variation of the standard single pole switch which controls a light only from one locationa third type is the four way switch which is used in conjunction with two three way switches to control lighting from more than two locationsthis configuration may be used in open plan homes or in large kitchens or great rooms where a central bank of lighting fixtures might.
The switch operates from two locations such as upstairs and downstairs but there are three ways it can be set. Because it uses two switches and one appliance. Three way switch has to do with the original identification of how the wiring was brought into the configuration when 3 way switches were first developed. So why is it called a 3 way switch. John for three or more location switching to work you require a 3 way switch at the both the beginning and the end of the switching loop the origination and the termination of the traveler conduductor for the switch loop circuit and 4 way switches at least one in the center in between those 3 way switches. The next most common is the three way switch which is commonly used to control a light fixture from two different locations.