What is the proper symbol for a single-pole switch?

• A. S
• B. SP
• C. SW
• D. Single

Answer: (A)

In schematic labeling, components are abbreviated with letters that quickly identify what they are. For a device that simply opens or closes a single circuit path, the standard label is the letter S, standing for switch. This keeps diagrams clean and unambiguous in straightforward circuits, and it directly signals you’re looking at a switch without implying extra details like how many poles or throws the device has. The actual symbol on the diagram would show a single contact that can open or close a single conductor. Other labels like SP, SW, or the word “Single” either add extra, unnecessary nuance or aren’t as universally recognized in basic schematic conventions, so S is the most straightforward and widely understood choice.