The 4 way switch symbol represents a double-pole, double-throw (DPDT) mechanism used to control a single lighting load from three or more locations. Because it functions as a reversing switch positioned between two 3-way (SPDT) switches, its schematic representation varies significantly between North American NEC blueprints and international IEC diagrams. Below is the complete reference data for identifying, interpreting, and troubleshooting these symbols in the field.
Standard 4 Way Switch Symbols by Region
Before pulling wire or terminating travelers, you must identify which drafting standard the architect or engineer used. The table below maps the schematic symbol to its physical terminal equivalents across the three major global standards. Note that NEC-style guidance applies to US/Canada, while IEC applies to most of Europe, Asia, and Australia. Your local AHJ (Authority Having Jurisdiction) has final authority on code compliance.
| Standard / Region | Symbol Name & Visual Description | Schematic Representation | Physical Terminal Mapping |
|---|---|---|---|
| NEC (US / Canada) | DPDT Switch with Crossing Lines. Visually appears as two single-pole switches stacked vertically with a dashed mechanical link. | Two parallel switch contacts with diagonal lines crossing between the input and output terminals, indicating path reversal. | 2 Brass screws (Line/Traveler In), 2 Dark/Black screws (Load/Traveler Out). Ground is green. |
| IEC 60617 (EU / Global) | Intermediate Switch (Symbol 07-04-02). Visually appears as an 'X' or an 'H' shape with diagonal cross-links. | A single switch box symbol with two inputs and two outputs, crossed internally to show the changeover state. | L1/L2 (Inputs), T1/T2 (Outputs). Earth terminal marked with standard ground symbol. |
| Old UK (Pre-2004 Colors) | Intermediate Switch (Legacy). Similar to IEC but drafted alongside legacy red/black/yellow conductor markers. | Identical to IEC 'X' symbol, but often annotated with 'C1/C2' for Commons and 'L1/L2' for strappers. | Common 1/2 (Inputs), L1/L2 (Outputs). Earth is bare copper sleeved in green/yellow. |
| NEMA (Industrial) | Drum Switch / Reversing Switch. Used for motor reversal rather than lighting, but electrically identical to a 4-way. | Rotary switch symbol with multiple contacts and a rotating wiper arm crossing the terminals. | L1/L2 (Line), T1/T2 (Load). Often includes 4 auxiliary contacts for control circuits. |
Which standard applies to you? If you are working on a residential or commercial building in North America, the blueprint will almost exclusively use the NEC/NEMA representations. If you are reading schematics for imported machinery, marine vessels, or working outside North America, default to the IEC 60617 standard. For a deeper look at North American drafting rules, refer to the NFPA 70 (National Electrical Code) guidelines.
Rows People Get Wrong: Common Schematic Misinterpretations
Even journeyman electricians and experienced DIYers misread 4-way schematics when transitioning between physical wiring and paper blueprints. Here are the specific rows and symbols that cause the most callbacks and short circuits.
Mistake 1: The "Crossed Travelers" Illusion in NEC Schematics
In the NEC 4 way switch symbol, the diagonal lines crossing in the middle of the symbol do not mean the physical traveler wires must cross over each other in the junction box. The crossing lines represent the internal mechanical linkage of the switch toggling between State A (straight through) and State B (reversed). When wiring a physical Leviton 5604 or Eaton 1744, you simply land the two travelers from the first 3-way switch on the brass terminals, and the two travelers going to the second 3-way switch on the dark terminals. The physical orientation of the wires in the box does not matter as long as the terminal pairs are respected.
Mistake 2: Confusing the IEC 'X' Symbol with a Crossover Junction
On IEC 60617 blueprints, the 4-way (intermediate) switch symbol looks like an 'X' or a bridge. Beginners often confuse this with a standard wire crossover junction where two conductors cross without connecting (which is usually denoted by a small semicircle "hop" in older drafts, or simply crossing lines with no node dot in modern CAD). If the 'X' is enclosed in a switch box outline or has a mechanical toggle line attached to it, it is a 4-way switch, not a wire junction.
Mistake 3: Ignoring the Mechanical Link Line
The NEC symbol features a dashed horizontal line connecting the two poles of the DPDT switch. This indicates that both poles switch simultaneously. If you see two separate SPDT (3-way) symbols on a blueprint without that dashed mechanical link, you are looking at two independent 3-way switches controlling two separate loads, not a single 4-way multi-location circuit.
Safe Interpretation When Switch Markings Are Faded or Missing
On the jobsite, you will frequently encounter older 4-way switches where the manufacturer's brass and dark terminal identification stickers have degraded, been painted over, or fallen off entirely. Safely interpreting the physical switch requires mapping the internal contacts using a multimeter.
How to map an unmarked 4-way switch using a Fluke 117 or Klein MM400:
- Isolate the Switch: Remove the switch from the circuit entirely. Do not attempt continuity testing with wires still attached, as parallel paths through the lighting load will give false readings.
- Set the DMM to Continuity: Select the continuity mode (the diode/soundwave symbol). Touch the probes together to verify the meter beeps.
- Identify the First Pair: Place one probe on a random terminal screw. Touch the other probe to the remaining three screws until you hear a beep. Mark these two screws with a piece of masking tape as "Pair A".
- Identify the Second Pair: The remaining two unmarked screws are "Pair B". Test them together to confirm they beep.
- Test the Toggle Action: Flip the switch toggle to the opposite position. Now, test one screw from Pair A against one screw from Pair B. You should get a beep. This confirms the internal crossover mechanism is functioning and reveals which terminals act as Line-in versus Load-out in the alternate state.
By mapping the pairs, you can confidently terminate the incoming travelers to one pair and the outgoing travelers to the other, regardless of the physical brass/dark color coding. For more on field-testing switches, the Mike Holt electrical training archives provide excellent continuity testing primers.
Frequently Asked Questions About 4 Way Switch Symbols
What does the 4 way switch symbol look like on a residential blueprint?
On a standard North American residential blueprint, the 4 way switch symbol is typically drawn as a standard single-pole switch symbol (a circle with a line and a toggle) but with a small "4" or "4W" printed next to it, or it is depicted as two parallel switch contacts linked by a dashed line. It will be shown on the wiring diagram situated linearly between two 3-way switch symbols, with four traveler wires connecting the sequence.
How is the 4 way switch symbol different from a 3 way switch symbol?
A 3-way switch is a Single-Pole, Double-Throw (SPDT) device. Its schematic symbol shows one common terminal branching into two possible traveler paths. A 4-way switch is a Double-Pole, Double-Throw (DPDT) device. Its symbol shows two separate input paths and two separate output paths that cross over each other. In practice, a 3-way switch has 3 terminal screws (plus ground), while a 4-way switch has 4 terminal screws (plus ground).
Can I use a 4 way switch symbol diagram to wire a smart switch?
No, you cannot directly wire a standard smart switch using a traditional 4-way schematic. Most smart lighting systems (like Lutron Caseta or Leviton Decora Smart) do not use physical traveler wires for multi-location control. Instead, you wire the smart switch at the primary line/load location and use wireless smart remotes (like the Lutron Pico) at the 3-way and 4-way locations. If you must use physical wired smart switches in a 4-way setup, you must purchase specific "Add-On" or "Companion" switches designed to communicate via low-voltage traveler wires, which requires a completely different wiring diagram than the standard NEC 4-way symbol.
Why does the IEC 4 way switch symbol look like an X or an H?
The IEC 60617 standard prioritizes functional representation over physical appearance. The 'X' or 'H' shape visually communicates the exact electrical function of the intermediate switch: taking two parallel input conductors and either passing them straight through (the 'H' state) or crossing them over (the 'X' state). This allows engineers reading the schematic in IEC-compliant regions to instantly understand the circuit's logic without needing to visualize the physical brass and dark terminal screws used in North American hardware.
