Hello
I don't understand the idea of 3-way switch.
Can someone help me?
Thanks

A "three-way" switch is also known as a single pole double-throw switch.

Basically it connects either of two inputs (but not both at the same time, of course) to an output.

Or looking at it the other way, it connects an input to either of two outputs (but not both at the same time, of course).

If we call the terminals 1, 2, and 3, then when the switch is up, 1 is internally connected to 2; when the switch is down, 1 is internally connected to 3.

Current cannot flow through the terminal that is not connected to 1. Thus 1 is referred to as the "common" terminal and is designated with a dark colored screw.


[This message has been edited by Dspark (edited 06-13-2001).]

Hi Mike

do you mean in terms of function as Dspark has detailed, or the name '3-way' ???

I'll bite. What's with "three-way?" Does it have anything to do with early double-throw switches having a center-off position?

I think 3 way is evolved from calling it a 3 wire switch, which I have heard older electricians call it. If there was a center off the switch would not be very functional for control at 2 locations and besides, with a position on each switch that is already off, why have a second?

To add a little more confusion--
A valve having one common port that diverts flow to either of two outlet ports is also called a 3-way (valve).

>Does it have anything to do with early double-throw switches having a center-off position?

That theory wouldn't go very far to explain a four-way switch.

Some three-way switches are as you describe. If you move the toggle carefully to the center, you can deenergize both outputs.

[This message has been edited by Dspark (edited 06-14-2001).]

>To add a little more confusion--
Actually, this is a least consistent...

>A valve having one common port that diverts flow to either of two outlet ports is also called a 3-way (valve).

Are there 4-way valves?

Anyway, a one-way valve lets fluid flow in one direction. A one-way switch isn't really possible with 60 Hz AC current.

A regular valve (two-way) technically lets fluid flow in either direction. A two-way switch lets electric current flow in either direction.

A three-way valve or switch allows flow in any two of three possible directions at a time.

A four-way switch allows flow in any four of eight possible directions at a time.


I definitely like the terms 2-wire, 3-wire, and 4-wire better.

Redsy;
that's just too much fun....i've just gotta hit up the next plumber i see with that one!

According to Jack Benfield, of Benfield Bender fame, the English call wires "ways" and since there are three conductors, it is a 3 way switch. Can't vouch for how true this is, but it sounds reasonable.

Tom

[This message has been edited by Tom (edited 06-14-2001).]