Re: gEDA-user: spdt, spst

[Karel Kulhavy <clock@xxxxxxxxxxxxx>]

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<