Switch (3-Way) Symbol
Definition: The Switch (3-Way) symbol represents a single-pole double-throw (SPDT) wall switch used in residential and commercial wiring to control a lighting fixture from two separate locations, featuring one Common terminal and two Traveler terminals; it is classified under IEC 60617-07 as a changeover switch and called a two-way switch in IEC (UK/European) practice, or a three-way switch in North American NEC / ANSI terminology.
Also known as: three-way switch, two-way switch (IEC/UK), SPDT switch, staircase switch, multiway switch.
What the Switch (3-Way) symbol means
The 3-Way Switch symbol denotes a switching device that connects its Common terminal to either Traveler 1 or Traveler 2, but never simultaneously to both. When two 3-way switches are wired together with the travelers cross-connected, toggling either switch changes the state of the controlled load regardless of the other switch's position — the classic use case is controlling a hallway or staircase light from two locations (top and bottom of stairs, or either end of a corridor).
In a wiring diagram, the 3-way switch symbol signals that this switch is one part of a multi-point control circuit; the presence of the Common terminal (where the switched live or load connects) and two Traveler terminals (the cross-connected legs running between switch locations) is the key identifying feature that distinguishes it from a standard single-pole switch.
How to identify the Switch (3-Way) symbol
The 3-Way Switch symbol is drawn as a single-pole switch arc (a line pivoting at a hinge point) with two fixed contact points instead of one, representing the two throw positions. The Common terminal is connected at the hinge (pivot) side and the two Traveler terminals are on the right side of the symbol. In wiring diagrams this is sometimes shown as an SPDT symbol — a common rail with two angled contact lines representing the two travel positions. The schematic SPDT symbol is a line with a pivot connecting to one of two parallel contact stubs.
Function in a circuit
A 3-way switch mechanically connects its Common terminal to one of its two Traveler terminals depending on toggle position. When used in pairs (two 3-way switches) with their traveler conductors cross-connected, the circuit allows the common load to be switched on or off from either location independently. For three or more control points, a 4-way (intermediate) switch is inserted between the two 3-way switches.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-07 classifies this as a two-position changeover (transfer) switch or two-way switch. The IEC symbol for a single-pole changeover switch is an arc pivoting from one contact that can swing to connect with either of two fixed contacts. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315 classifies this as a single-pole double-throw (SPDT) switch. North American residential wiring practice (NFPA 70 / NEC) uses the term 'three-way switch' for this device. The ANSI switch symbol is a movable contact line pivoting between two fixed contact points. |
| Key difference | The glyph is the same SPDT/changeover symbol in both IEC and ANSI; the naming differs — 'two-way switch' in IEC/UK/European practice versus 'three-way switch' in North American NEC practice. The counting convention differs: IEC counts 'ways' as throw positions (2 throws), while NEC counts the terminal count (common + 2 travelers = 3 terminals = '3-way'). |
Terminals / pins
| Pin | Name |
|---|---|
| common | Common |
| traveler1 | Traveler 1 |
| traveler2 | Traveler 2 |
Typical values
Typical ratings: 15 A at 120/277 V AC (NEMA, residential), 10 A at 250 V AC (IEC). Conductor terminals: 1× Common, 2× Traveler. Toggle positions: 2 (SPDT). Common North American wire gauges: 14 AWG (15 A circuit) or 12 AWG (20 A circuit). Traveler conductors: 3-wire cable (2 travelers + ground) between switch locations.
Where the Switch (3-Way) symbol is used
- Staircase lighting controlled from both top and bottom landings
- Hallway lights with switches at each end of a long corridor
- Garage entry lighting controllable from inside the garage and from the house door
- Bedroom overhead lighting controlled from the room entry door and from the bed location
- Outdoor pathway lighting controllable from front door and back door
- Hotel corridor lighting systems where lights must be operated from multiple points
- Industrial access aisles requiring lighting control at both ends for safety egress
Example
In a residential staircase wiring diagram, two 3-Way Switch symbols appear — one at the bottom landing and one at the top landing. The Common terminal of the lower switch connects to the switched live feed; the Common terminal of the upper switch connects to the ceiling light fixture. The two Traveler terminals of each switch are cross-connected by a 3-conductor cable running between the switch boxes. Toggling either switch changes the light state regardless of the other switch's position.
Key facts
- The 3-Way Switch (North American terminology) is a single-pole double-throw (SPDT) changeover switch with one Common terminal and two Traveler terminals, used to control a load from two locations.
- In IEC / UK / European terminology, this same device is called a 'two-way switch' — the naming difference refers to the number of terminal pairs (IEC) versus the total terminal count (NEC).
- The symbol is drawn as an SPDT switch: a movable contact line at the Common terminal pivoting to connect to either Traveler 1 or Traveler 2, per IEC 60617-07 and ANSI Y32.2 / IEEE 315.
- Two 3-way switches are required to control a single load from two locations; for three or more control points, one or more 4-way (intermediate) switches are inserted between the two 3-way switches.
- The Common terminal carries the switched live (hot) conductor or the load conductor, while the Traveler terminals connect to the matching travelers of the paired 3-way switch via a 3-wire cable.
- Rated at 15 A / 120 V AC (NEMA residential) or 10 A / 250 V AC (IEC), these switches are used for lighting loads including incandescent, CFL, LED, and fluorescent fixtures.
- Smart 3-way switches (Wi-Fi or Z-Wave) use a 3-way switch wiring scheme but communicate wirelessly; only one switch needs a neutral wire while the other can use the existing traveler cables.
Diagrams that use this symbol
- 3 way switch wiring
- wiring a three way switch
- 3 way switch wiring diagram
- 3 way switch wiring schematic
- three way switch connection diagram
- three way switch wiring diagram
- 3 way switch diagram
- three way switch diagram
Frequently asked questions
What does the 3-way switch symbol mean in a wiring diagram?
The 3-Way Switch symbol represents a single-pole double-throw (SPDT) switch that can control a lighting load from two separate locations. It has one Common terminal and two Traveler terminals. When two 3-way switch symbols appear in a diagram with their travelers cross-connected, either switch can turn the load on or off regardless of the other switch's position.
What does the 3-way switch symbol look like?
The 3-way switch symbol is drawn as an SPDT (single-pole double-throw) switch: a movable contact line pivoting from the Common terminal with two fixed contact stubs representing Traveler 1 and Traveler 2. In residential wiring diagrams it is often shown as a rectangular box labelled '3-way' with three terminals. The schematic SPDT symbol shows the pivot/arc between two contacts rather than one.
What is the difference between a 3-way switch and a 2-way switch?
In North American NEC terminology, a '3-way switch' is an SPDT switch (1 common + 2 travelers = 3 terminals); a '2-way switch' is a standard single-pole on/off switch (2 terminals, 1 pole). In IEC / UK terminology, what Americans call a '3-way switch' is called a 'two-way switch'; the UK '2-way switch' refers to the same SPDT device. Confusingly, what Americans call a '2-way switch' is a UK 'one-way switch'.
What is the Common terminal on a 3-way switch?
The Common terminal is the terminal that always carries current — it connects to either the incoming hot (feed wire) at one switch or to the load (light fixture) at the other switch in a 3-way circuit. The Common terminal is usually a different colour (black screw) from the two Traveler terminals (brass screws). Mis-wiring the Common terminal to a Traveler position is the most common 3-way switch installation error.
How do you wire two 3-way switches to control one light?
Connect the hot (black) wire from the power source to the Common terminal of the first 3-way switch. Run a 3-wire cable (black, red, white) between the two switches, connecting black-to-Traveler 1 and red-to-Traveler 2 at both switches. Connect the Common terminal of the second switch to the light fixture's hot wire. Connect the neutral (white) wire directly from the power source to the light fixture neutral. This creates the standard two-location control circuit.
What standard defines the 3-way switch symbol?
The 3-way switch uses the SPDT (single-pole double-throw) changeover switch symbol defined in IEC 60617-07 (switching devices) and ANSI Y32.2 / IEEE 315 (graphic symbols for electrical diagrams). Installation requirements for 3-way switch wiring in North America are covered by NEC (NFPA 70) Article 404.
Can a 3-way switch be used as a regular on/off switch?
Yes. A 3-way switch can function as a simple SPST (single-pole single-throw) on/off switch by using the Common terminal and only one of the two Traveler terminals, and leaving the other Traveler terminal unconnected. This is occasionally done when a 3-way switch is available and a standard switch is needed, though it wastes one terminal position.
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