3 screws means 3-way
4 screws means 4-way
I also note, and like, the hot and neutral being labeled as "main".From a 1921 Arrow-Hart catalog:
The text says 'point', but the diagram says 'way'. Maybe back in those days the terms were used interchageably, and 'way' eventually won out.
Oh, stop it! grinWhat about SPST Center-Off?
What about DPST? SPTT?
Call Mr. C. and tell him you can do it if you turn one switch upside down and fashion a handle-tie so they operate together.My teacher used to offer a reward to the student who could make 2 single pole switches work like a 3 way. Yes people tried. no not me. Thanks Mr C. from jackson voc.