Re: gEDA-user: spdt, spst

[Bert Douglas <bertd@xxxxxxxxxxxxx>]

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.



Karel Kulhavy wrote:
> On Wed, Jan 19, 2005 at 10:22:44AM -0800, John Luciani wrote:
>
> > SPST ..... Single Pole, Single Throw
> > SPDT ..... Single Pole, Double Throw
>
>
> What does "pole" and "throw" mean? I know just what north and south pole is.
> And also telephone pole.
>
> Cl<