Two-way stair light

Scenario

A stair or hallway lamp must be operable from either end. That requires a changeover switch at each location and two traveler conductors between them; two ordinary on/off switches in series do not provide the same behavior.

Annotation key

• Both S1 and S2 use type=switch_spdt, exposing one common and two throws.
• traveler_a and traveler_b connect the two throws of the switches.
• feed is the fused live common on S1; switched is the lamp-side common on S2; 0 is the bonded neutral reference.
• L1 ... type=lamp uses a load-appropriate designator and the lamp symbol.

How to read

Each switch selects one traveler. The lamp is energized when both switches select the same continuous path and de-energized when they select different paths, so changing either switch changes the lamp state. The bonded neutral reference 0 returns directly from the lamp to the source on the lower rail.