Single-pole switch
An ordinary light switch that controls a light from one place. Plans mark it with the letter S.
This explains what a symbol represents on a drawing. Conventions vary between firms and standards, and a drawing's own legend takes precedence.
How to read it
NECA 100 lists the single pole switch first among its switch symbols, before the double pole, three-way and four-way switches. The Army's print-reading manual gives the same order, marking the others with S2 and S3.
Also searched as: light switch symbol, switch S.
Look-alikes
An S with a small 3 is a three-way switch.
More blueprint symbols
Sources
- Symbols for Electrical Construction Drawings, NECA 100-2013 (ANSI), National Electrical Contractors Association, sec. 4.0, symbol 4.001
- Construction Print Reading in the Field, TM 5-704 / AFM 85-27, Departments of the Army and the Air Force, fig. 3-32; app. B, fig. B-9
- Reading Architects' Blueprints, William S. Lowndes, 1922, International Textbook Company, Scranton (Internet Archive), §6, art. 44
Last reviewed September 24, 2026 by Rory Hansen. How we research