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Navettes

Travellers are the two conductors that run between the switches in a 3-way or 4-way circuit. Each switch chooses which traveller it connects to; the light is on when the switches at both ends agree on the same one. Also spelled “traveler”.

What the switches do with them

A 3-way switch has one common terminal and two traveller terminals. Flipping it moves the common from one traveller to the other. At the first switch the common takes the incoming hot; at the last it becomes the switched hot to the light. A 4-way switch sits between them and either passes the travellers straight through or crosses them over — which is how any number of 4-ways let a light be switched from more than two places.

Finding them on a switch

On most 3-way switches the two traveller screws are the same colour and the common is the odd one out, often darker. Do not trust the position — look at the colour or the marking. On an old switch with no marking, a continuity tester finds the common: it is the terminal that connects to one screw in each position of the toggle.

One worked, so the idea sticks

Why the light goes on and off

  1. Two 3-way switches, S1 and S2, with travellers T1 and T2 between them.
  2. S1 connects the hot to T1; S2 connects its common to T1. Both on T1: a path — the light is on.
  3. Flip S2: its common moves to T2. S1 is still on T1. No path — the light is off.
  4. Flip S1: it moves to T2. Now both are on T2 — on again. Either switch changes the state, from either end.

The interactive 3-way diagram lets you flip both switches and watch the path.

Questions fréquentes

Can a traveller be the white conductor of a cable?

It can, when the cable’s conductors are used that way — and then it has to be re-identified as an ungrounded conductor. How it must be marked is a code rule, so check your book.

Why does my 3-way only work when the other switch is in one position?

Almost always a traveller and the common have been swapped at one switch. Find the common with a tester and re-land it; the colour of the wire is not proof.

How many travellers does a 4-way need?

Two in and two out — four traveller conductors land on a 4-way, and nothing else does.

Voir aussi

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