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<