# Intermediate light switch plan mark

Canonical URL: https://eloragrid.ai/symbols/iec-intermediate-light-switch
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: SI
Drawing use: GA
Reference families: IEC

## Symbol convention

Convention: IEC
Form: Intermediate switch
IEC 60617 installation-plan style (architectural and topographical installation symbols); independently drawn, not certified IEC geometry or a database identifier.

Plan mark for an intermediate switch inserted between two two-way switches to add a third control point.

## In plain English

### What does Intermediate light switch plan mark mean?

An intermediate switch reverses the connection of the two strapping conductors between a pair of two-way switches, so any number of intermediate switches can be added along a corridor. The plan form uses crossing strokes through the switch circle to suggest the crossover action.

### A simple example

On long corridors, open-plan stairs and large rooms with several doors, plans show two two-way switches at the ends and intermediate switches at the middle doors. Reading the switching lines confirms which group each set controls.

### What the drawings help you do

The symbol does not give contact arrangement detail or rating. Its presence also implies four-core or two-strapper wiring, which the installer must plan for.

### This particular reference

Plan mark for an intermediate switch inserted between two two-way switches to add a third control point. A two-way switch has a changeover contact; an intermediate switch crosses two strappers and is useless without two-way switches either side.

### Terms

- Normally open / normally closed: The contact state in the normal condition defined for the drawing.
- Terminal: An identified point where a conductor connects.
- Rating: A value stating the conditions for which equipment is specified.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)


## What it represents

An intermediate switch reverses the connection of the two strapping conductors between a pair of two-way switches, so any number of intermediate switches can be added along a corridor. The plan form uses crossing strokes through the switch circle to suggest the crossover action.
On long corridors, open-plan stairs and large rooms with several doors, plans show two two-way switches at the ends and intermediate switches at the middle doors. Reading the switching lines confirms which group each set controls.
The symbol does not give contact arrangement detail or rating. Its presence also implies four-core or two-strapper wiring, which the installer must plan for.

## How to read it

- Confirm the run has two-way switches at each end.
- Count control points to check the number of intermediates.

## Information to show or reference

- Show the two end switches and every intermediate.
- Link all to the controlled luminaires.
- Allow for strapper wiring in the cable schedule.

## Important distinction

A two-way switch has a changeover contact; an intermediate switch crosses two strappers and is useless without two-way switches either side.

## Facts

- Operation: Crossover of two strapping conductors
- US equivalent term: Four-way switch
- Exact standard graphic: Not reproduced here; confirm the form against IEC 60617 and the project legend

## Public references

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC graphical symbol context; independently drawn here.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.