On Wed, Jan 19, 2005 at 12:52:49PM -0600, Bert Douglas wrote: > pole = moving contact > throw = fixed contact > > The terminology is old, probably going back to the time of the > telegraph, perhaps 1850s. Or perhaps somewhat later at the time of > introduction of electric lights in 1880s. > > The first switches were exposed "knife" switches. You might see this in > a frankenstein movie. > > I am not sure why the moving contact is called a "pole". But I am > fairly sure I understand the origin of the term "throw". To avoid > arcing and shock, you would typically operate the switch by grabbing the > handle and rapidly "throwing" it towards the closed position.
But there can be spdt with 2 positions (ON-ON) and with 3 positions (ON-OFF-ON) how is this distinguished? Cl<
