why is a 3way sw called a 3way not a 2way

[mivey]

...The circuit can be extended by using multiple 4-way switches...

So it would appear the individual switch definition is not dependent on the number of switches installed.

 

[rattus]

Maybe:

Maybe:

Maybe '3-way' is a corruption of '3-wire' which would make more sense. Natheless, this term is used by electricians to describe a SPDT switch . The latter term is used universally in other sectors of the electrical and electronic industry.

Logicians would describe the 3-way circuit as an exclusivee-OR

'3-way' may be used to describe a single switch or the complete circuit..

 

[Rick Christopherson]

Logicians would describe the 3-way circuit as an exclusivee-OR

That's interesting Rattus, because I was thinking along those lines earlier tonight as a possible reason for the name "3-way" and the possible states of the circuit. 1) both on A = On, 2) both on B = On, 3) one on A and one on B = Off.

I know what you meant, however, a 3-way would be an AND circuit. The 4-way, in the crossed position, is the Exclusive-OR (kind of), but it's actually a NAND.

[edit] I corrected the mistakes of this post below.

 

[mivey]

...Oh and iwire is just man not a diety...

He could be diety, it is hard to tell from his picture. I'm trying to diet a little myself as I've added a few pounds over the years.

If you meant deity, I don't recall iwire apotheosizing or there being any deification ceremony here. He does admit some of his mistakes.

 

[mivey]

That's interesting Rattus, because I was thinking along those lines earlier tonight as a possible reason for the name "3-way" and the possible states of the circuit. 1) both on A = On, 2) both on B = On, 3) one on A and one on B = Off.

I know what you meant, however, a 3-way would be an AND circuit. The 4-way, in the crossed position, is the Exclusive-OR (kind of), but it's actually a NAND.

How would you describe the 4-way using this analogy? You would have to combine some states like you did with the 3-way.

[edit: the AND gate has a 3/1 output not a 2/2 output like the XOR so the XOR is a better choice for the 3-way, correct?]

 

[Rick Christopherson]

How would you describe the 4-way using this analogy? You would have to combine some states like you did with the 3-way.

Yup, that's why I didn't post the concept earlier. It would be too hard to justify or explain. I said I was "thinking about it", not that I claimed it was right. :grin:

[edit: the AND gate has a 3/1 output not a 2/2 output like the XOR so the XOR is a better choice for the 3-way, correct?]

I am not sure I follow what you are saying by 3/1 Vs 2/2, but I acknowledge that initially, I had been thinking XOR myself.

OH...... I get the 1/3 and 2/2 now....But no, this is not correct...That's what took me a while to figure out what you meant. What you are thinking (I think) is an XNOR. As a matter of fact, after giving this more thought, the switches would be more appropriately considered an XNOR, not the AND that I said previously.

Instead of the A & B I used above, consider A=Up=1, and B=Down=0:
0,0 = On
0,1 = Off
1,0 = Off
1,1 = On
This is an XNOR function, not an XOR function. Nevertheless, I now understand better where you (and Rattus) were coming from. I also acknowledge my original mistake with the AND function.

Geeze I am getting old and senile for my middle age. Logic was my main study, and I can't believe it took me this long to deduce the XNOR versus the AND.

Geeze I am getting old and senile for my middle age. Logic was my main study, and I can't believe it took me this long to deduce the XNOR versus the AND. Hey, didn't I just say that? :grin:

[edit] Just to add to my senility, if you flipped one of the 3-way switches upsidedown (as is common), then you would get the XOR function. Both Up or both Down would be an Off-state. In my feeble defense, it is still electrically an XNOR though.

 

[iwire]

#24 this thread.

Clint argues with me for two hours and now I find, he too says it's a two way switch.

Different subjects, once we get this first misconception you have straighted out I will be glad to discuss post #24

My disagreement with you here is that you feel a 3-way switch is a system of at least two interconnected devices.

A three way switch is a system that controls a load with two switches. It just so happens that two components of the switching system are SPDT switches.

A 3-way switch is a single device, a few of us have provided outside sources to back that up.

Still waiting on any outside sources from you.

 

[iwire]

He could be diety, it is hard to tell from his picture. I'm trying to diet a little myself as I've added a few pounds over the years.

I should be more diety.

 

[dwcaveney]

DELETED

 

[roger]

You will be waiting a long time, None coming.

So, you don't have any back up to substantiate your argument?


Roger

 

[480sparky]

Your definition of a three way switch is a misnomer.

Then apparently you are the only one in the nation who has it correct.


So now it is official. The retired carpenter has spoken. There is no such thing a three-way switch. They are now, and forevermore, to be called a two-way switch. Everyone, remember what you were doing on this historic date. Pearl Harbor.... Kennedy's assassinatinon.... Sept. 11..... and the Great 3-way Debate will all be permanently etched in your minds.



I'll start writing proposals to change all the references in the NEC.

I need someone to volunteer to help rewrite the UL White book.

Someone needs to contact all the manufacturers of these devices and let them know they are using incorrect terminology.

And we've got millions of books out there that have it wrong as well.... The NEC handbook, Ugly's, DIT books, etc. etc.

How many of you out there are using estimating software? You'll need to change all the entries for bidding 3-ways to 2-ways.

And the supply houses. Oh my! Are those counter guys ever gonna get it right?

Oh, and all those web sites out there that state 3-way.... they're gonna need updated.









Now, dw, you wanna take on 4-ways?

 

[rattus]

Oops!

Oops!

How would you describe the 4-way using this analogy? You would have to combine some states like you did with the 3-way.

[edit: the AND gate has a 3/1 output not a 2/2 output like the XOR so the XOR is a better choice for the 3-way, correct?]

Actually, a two-switch system would be describe as an exclusive-NOR.

C = AB + A'B'

If C = 1, the light is ON.

The states are 00, 01, 10, and 11

I don't know what to call it but, each 4-way (DPDT) would double the number of states, i. e.,

000, 001, 010, 011, 100, 101, 110, 111

But who has time to worry about that?

 

[iwire]

You will be waiting a long time, None coming.

OK, until such time you provide any back up to your view up we will consider your opinion to be wrong, misinformed etc.

Of course most of us already knew that.

 

[dwcaveney]

DELETED

 

[dwcaveney]

DELETE

 

[rattus]

Oh sparky,
Come on, with your intelligence,experience and logical mind, you could re-write all that stuff in 10 minutes.
However you don't have to, people accept the use of misnomers every second, of every day. We know what three way switch means at the order desk. Electrically it's not a three way switch. And no matter what you say it never will be.

EDIT: You know why? Because a SPTT is a three way switch

I think "three-way" has no precise definition, but the the typical electrician doesn't know that, doesn't need to know that, and doesn't care. So what's the problem?

 

[roger]

You know three way switch is a misnomer. By the way where do I find the the rule on when and how to edit my posts. Ask You?

If you make a statement you should be able to back it up with something more than your opinion and if you don't have a way to back it up you should state that your views are your opinion, this is normally done by typing this, "IMO" somewhere in your post.

Personally I don't care what this switch is called any more than I care about why "Hamburger" is called hamburger but is made from Beef.

As far as editing etiquette click HERE


Roger

 

[dwcaveney]

DELETED Roger[/QUOTE]

 

[dwcaveney]

I think "three-way" has no precise definition, but the the typical electrician doesn't know that, doesn't need to know that, and doesn't care. So what's the problem?

Rattus,
No problem, just the distinction between electrical and colloquial.
DW

 

[dwcaveney]

Issue of Fact

Issue of Fact

So, you don't have any back up to substantiate your argument?

Roger

If eveyone in the world knows that there is a stop sign at Fourth and Elm. Does the cop have to prove to the jury, there is a stop sign there, or just the issue of fact, that you ran it?

EDIT: Sorry I might be beating a dead horse.