"Wilma Harrington" wrote in message
...
In article , BP
wrote:

"Goedjn" wrote in message
...
On Fri, 17 Feb 2006 11:20:56 -0600, Bud--
wrote:

BP wrote:
The semantics here are getting garbled: If one of the switches on the
duplex
device works a light along with another switch located somewhere
else,
that
is a 2-way function. A 1-way switch has two screws (poles, lugs). a
2-way
has 3 screws, a 3-or-more-way has 4 screws (all assuming only one
switch
on
the device, not duplex).
HTH


That is eminently reasonable but in the US 2 switches controlling a
light from 2 positions uses 3-way switches with, as you said, 3
terminals each.

Control from 3 or more positions uses 2 3-way switches plus as many
4-way switches as needed. As you said 4-way switches have 4 terminals.



A good reason to learn and use the technical terms "pole" and "throw".

A pole is how many switch-arms a lever controls, and a throw is
how many different contacts that arm can reach.

So a SPST (SIngle-Pole-Single-throw) is 1 circut, either
open, or closed. a SPDT is what most people call a two-way,
where you have one in (or out) selecting between two outs
(or ins). A DPDT is the one that confuses people...
Many modern ones apparently only have four terminals
on them, and are straight-through if the switch is one way,
and crossover if it's the other. The ones I learned on
had six terminals, one at the base of each switch-arm,
and four more at the top and bottom, which means on one
hand that you can use them for anything, but on the other
hand, it always takes me 15 minutes with graph paper
to figure out how.

There is probably no area of construction where there is more confusion
of
terminology than electrical. It is always amazing to hear the different
variations. And only in electrical terms can you have "ivory" be the
darker
color, and "almond" be the lighter. Completely counter-intuitive.
As a builder I like to keep it simple: a one way switch switches one way:
from a single location. A two way switch switches two ways: from two
locations. How many poles are not my problem, man. That's the
electricians
job!



Yikes, I'm going to cut and paste this whole thread into a new page and
then me and my new Mac are, with the help of Mr. Google, see if I can
get a handle on the vocabulary and theory of how it's all supposed to
work.

Did I mention that the upstairs room my computer is in, is on the same
circuit that the kitchen lights are on?

Perfectly normal, compliant, and a great way to reduce costs.