The answer in two lines
A two-way switch lets you turn one light on and off from two places, such as the top and bottom of a staircase. For a third place or more, an intermediate switch goes between the two. The two switches are linked by two traveller wires, and the intermediate switch passes them straight or crosses them. Terminal names differ by maker, so follow the diagram printed on the switch and use a qualified electrician.
Want to switch the hallway light on at one end and off at the other, or turn the bedroom light off from bed? This guide from Tawredaat (توريدات), an Egyptian supplier of electrical and finishing materials in Cairo and Giza, explains the idea in words and a simple table, and when you need an intermediate switch, using the sources listed at the end.
Safety note
⚠ Switch off the circuit breaker for the circuit at the consumer unit first, and confirm the circuit is dead with an approved voltage tester before touching any wire (HomeServe, Able Group). Wiring should be done by a qualified electrician, because incorrect installation can cause electric shock or fire (Legrand). This guide is for understanding only and does not replace the maker's diagram.
What is a two-way switch and how does it control one light from two places?
A two-way switch has three terminals: a common terminal (C or COM) and two others called L1 and L2 (Schneider, Simon). Flipping it connects the common to one of the two terminals; it does not cut the current but redirects it (Simon). You need two of them, one at each place.
Per Wikipedia, the supply goes to the common of the first switch, two traveller wires link the two switches, and the common of the second switch goes to the lamp. Flipping either switch changes the lamp state: there are four switch-position combinations, two on and two off.
| Part | What it does | Note |
|---|---|---|
| Common (C or COM) | The shared terminal: one takes the supply (first switch), the other goes to the lamp | Name and position vary by maker; follow the diagram printed on the switch |
| L1 and L2 | The two terminals the common switches between | Simon and Schneider use these names; other makers use other marks |
| Two traveller wires | Link L1 to L1 and L2 to L2 between the switches | Carry the path chosen by the first switch to the second (Schneider) |
How does it work in plain words?
- ✔ The first switch chooses which traveller wire carries the current.
- ✔ The second switch checks whether it is on the same wire: if yes the circuit completes and the light is on; if not, it stays off.
- ✔ That is why either switch can change the state, whatever position the other is in.
When do I need an intermediate switch?
When you want to control the same light from 3 places or more (for example the start, middle and end of a corridor). An intermediate switch goes between two two-way switches and either "crosses or keeps straight" the traveller wires (Simon). It has 4 terminals, two in and two out, and you can add one for each extra place (Simon, Wikipedia).
| Places | Switches needed | Note |
|---|---|---|
| One place | One 1-way switch | The normal case: one switch per light |
| Two places (hallway, stairs, bedroom) | Two 2-way switches | Two traveller wires between them |
| Three places | Two 2-way switches + one intermediate between them | Intermediate in the middle |
| Four or more places | Two 2-way switches + one intermediate for each extra place | Simon: add as many as you need |
How do I check the terminals on my own switch?
- ✔ Read the diagram printed on the back of the switch or in its instruction sheet: terminal names (C, L1, L2 or other marks) differ by maker.
- ✔ Photograph the existing wiring before disconnecting and note where each wire goes (Able Group).
- ✔ Check the switch type (1-way, 2-way or intermediate) from the product name and the packaging before installing.
- ⚠ In multi-way circuits wrong wiring can leave some conductors live even with a breaker off; leave this to a qualified electrician (Able Group).
- ⚠ Wire sizes must be standard (1.5, 2.5, 4, 6 or 10 mm²) and chosen by a qualified electrician according to the load and breaker. For the general principle see our breakers and wire sizes guide.
1-way, 2-way and intermediate switches available at Tawredaat
Currently listed from Legrand Arteor: Legrand Arteor 1-Way Switch 10AX 250V - White (1 Module), Legrand Arteor 2-Way Switch 10AX 250V - 1 Module - White Finish and Legrand Arteor Intermediate Switch - 1 Module, 10AX 250V, White Finish. Our product pages give the name and finish only, so follow the maker's diagram printed on the switch and ask a qualified electrician before installing. See also all switches and sockets, the switches and sockets buying guide, the dimmer and LED bulb guide and the curtain and roller shutter switch guide. For circuit safety see the RCCB earth leakage breaker guide and the earth wire guide.
Frequently asked questions
What is the difference between a 1-way and a 2-way switch?
A 1-way switch opens and closes one circuit, so it controls from one place. A 2-way switch redirects the current between two terminals, so with a second one you control the light from two places.
Can I use two 1-way switches instead of 2-way?
No. Two 1-way switches will not give correct control from two places, because each one only opens or closes. You need two 2-way switches.
When do I use the intermediate switch?
When you need to control the same light from a third place or more. It goes between two 2-way switches and crosses or passes the two traveller wires.
Are the terminal names C, L1 and L2 universal?
No. Names and layout differ by maker. Follow the diagram printed on the switch and its instruction sheet, and let a qualified electrician connect it.
Can I fit it myself if I switch off the breaker?
Isolating the breaker and proving the circuit dead is essential, but correct wiring needs a qualified electrician, since mistakes can cause shock or fire.
Do the wires between the switches need a specific size?
Standard sizes are 1.5, 2.5, 4, 6 and 10 mm², chosen by a qualified electrician from the load and breaker. We do not state a size or voltage ourselves.
Need 2-way and intermediate switches?
Browse switches and sockets at Tawredaat, with delivery in Cairo and Giza.
About Tawredaat: Tawredaat (توريدات) is an Egyptian supplier of electrical and finishing materials, serving homeowners, companies and contractors in Cairo and Giza. Questions? See our FAQ.
Sources
- Wikipedia, Multiway switching (two SPDT switches for control from two places, the travellers, and the 4-way intermediate switch) — en.wikipedia.org/wiki/Multiway_switching
- Simon Electric, Two-way switch wiring diagram explained (common, L1 and L2, two traveller wires, the intermediate switch has 4 terminals) — simonelectric.com/en-ad/blog/two-way-switch-wiring-diagram-explained
- Schneider Electric eShop, What is a two-way switch (3 terminals C, L1 and L2, the two switches linked by two wires) — eshop.se.com/in/blog/post/two-way-switch.html
- Legrand, intermediate switch instruction sheet (installation preferably by a qualified electrician; wrong installation may cause shock or fire) — assets.legrand.com/pim/NP-FT-GT/LE12391AA.pdf
- HomeServe, How to replace a light switch (switch off the circuit breaker and prove the circuit dead with an approved tester) — homeserve.co.uk/living/electrical/how-to-replace-a-light-switch
- Able Group, How to change a light switch (isolate at the consumer unit, photograph the wiring before disconnecting, use a qualified electrician) — able-group.co.uk/advice-hub/how-to-change-a-light-switch
- Tawredaat product pages (name and finish only) — tawredaat.com/collections/switches-sockets
