This is useful in long hallways that may need more than one light to be controlled by the two switches, and which may also have receptacles needing unswitched power as well as the switched lights.

An optional receptacle can be connected at Terminal B, since that terminal is always live.Īn alternative system, known as the 'California 3-way', or 'coast 3-way' connection system allows both switched and unswitched loads to be connected near both switches without running too many additional wires. An optional additional lamp can be connected at Terminal A as a pilot lamp, or to illuminate a long corridor. Using the traveler system, there are four possible permutations of switch positions: two with the light on and two with the light off.Īlternative system The 'California 3-way' or 'Coast 3-way' connection never connects the lamp socket shell to the line (hot) terminal. The switches are then connected to each other by a pair of wires called 'travelers' (or 'strappers' in the UK), and the lamp is connected to the common terminal of the second switch, as shown. In the traveler system, also called the 'common' system, the power line (hot, shown in red) is fed into the common terminal of one of the switches. There are several arrangements of wiring to achieve this. Switching a load on or off from two locations (for instance, turning a light on or off from either end of a flight of stairs) requires two SPDT switches. Toggling any switch changes the state of the load from off to on, or from on to off. An intermediate switch can, however, be implemented by adding appropriate external wiring to an ordinary (six terminal) DPDT switch, or by using a separate DPDT relay.īy connecting one or more 4-way (intermediate) switches in-line, with 3-way switches at either end, the load can be controlled from three or more locations. This switch has two pairs of 'traveler' terminals that it connects either straight through, or crossed over (transposed, or swapped). Ī '4-way' (intermediate) switch is a purpose built double pole, double throw (DPDT) switch, internally wired in manufacture to reverse the connections between the input and output and having only four external terminals. The switches may be arranged so that they are in the same orientation for off, and contrasting orientations for on. By correctly connecting two of these switches together, toggling either switch changes the state of the load from off to on, or vice versa. Toggling the switch disconnects one 'traveler' terminal and connects the other.Įlectrically, a typical '3-way' switch is a single pole, double throw (SPDT) switch. These switches appear externally similar to single pole, single throw (SPST) switches, but have extra connections which allow a circuit to be controlled from multiple locations. Three-way and four-way switches make it possible to control a light from multiple locations, such as the top and bottom of a stairway, either end of a long hallway, or multiple doorways into a large room. The electrical load may be permanently hard-wired, or plugged into a switched receptacle. The controlled load is often a lamp, but multiway switching is used to control other electrical loads, such as an electrical outlet, fans, pumps, heaters or other appliances. Readers in most other countries should read 'two-way' or 'SPDT' for the United States 'three-way' and 'intermediate', 'crossover' or 'DPDT' switch for the United States 'four-way'. This article follows usage in the United States. Three-way and four-way switches A double pole, double throw switch wired to act as a four-way (intermediate or crossover) switch In alternative designs, low-voltage relay or electronic controls can be used to switch electrical loads, sometimes without the extra power wires. Double pole, double throw (DPDT) switches allow control from three or more locations. When the load is controlled from only two points, single pole, double throw (SPDT) switches are used.

In contrast to a simple light switch, which is a single pole, single throw (SPST) switch, multiway switching uses switches with one or more additional contacts and two or more wires are run between the switches. A common application is in lighting, where it allows the control of lamps from multiple locations, for example in a hallway, stairwell, or large room. In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load from more than one location. JSTOR ( April 2021) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: 'Multiway switching' – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.

Low voltage light switch wiring diagram