"Jeff Liebermann" wrote in message
...
On Thu, 31 Oct 2013 20:15:57 +0100, Leif Neland
wrote:

No connection is NC

True. Unfortunately, this doesn't solve any of the problems and
questions I mentioned.

Rhetorical question: What's the schematic symbol for a center off
switch? I couldn't find anything definitive:
http://www.edrawsoft.com/switch-symbols.php

I'd make the viper of the switch rest on a non-connected dot or circle.

I was hoping to find something in IEC 60617 or ANSI Y32.16 specs.

Incidentally, the proper designation seems to be SPCO (single pole
center off)

SPCO can also stand for Single Pole Change Over ... :-(

Arfa

On Fri, 1 Nov 2013 02:36:16 -0000, "Arfa Daily"
wrote:

"Jeff Liebermann" wrote in message
Incidentally, the proper designation seems to be SPCO (single pole
center off)

SPCO can also stand for Single Pole Change Over ... :-(
Arfa

How about SPMO (Single Pole Middle Off)?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Thu, 31 Oct 2013 07:34:21 -0700 "William Sommerwerck"
wrote in Message id:
:

"JW" wrote in message news On Wed, 30 Oct 2013 20:19:51 +0000 (UTC) Jerry Peters
wrote in Message id: :

There are 3 position wall switches available. The middle position puts
a diode in series to dim the lights, full-on bypasses the diode. My
parents had one of these switches in their dining room, until the
diode opened, when it was replaced with a regular dimmer.

Odd, I have one of those in the bathroom, but the *center* position is
off. Probably from the 1930's or 1940's, but I'm just guessing.

So there are two ON positions and one OFF?

Yes, one of the on positions is dim, the other full bright. I assume
there's a diode in there.

Odd, I have one of those in the bathroom, but the *center*
position is off. Probably from the 1930's or 1940's, but I'm
just guessing.

So there are two ON positions and one OFF?

Yes, one of the on positions is dim, the other full bright.
I assume there's a diode in there.

The diode would have to be a selenium rectifier.

"William Sommerwerck" wrote in message
...
Odd, I have one of those in the bathroom, but the *center*
position is off. Probably from the 1930's or 1940's, but I'm
just guessing.

So there are two ON positions and one OFF?

Yes, one of the on positions is dim, the other full bright.
I assume there's a diode in there.

The diode would have to be a selenium rectifier.


Why ?

Arfa

On Sat, 2 Nov 2013 03:08:45 -0000, "Arfa Daily"
wrote:



"William Sommerwerck" wrote in message
...
Odd, I have one of those in the bathroom, but the *center*
position is off. Probably from the 1930's or 1940's, but I'm
just guessing.

So there are two ON positions and one OFF?

Yes, one of the on positions is dim, the other full bright.
I assume there's a diode in there.

The diode would have to be a selenium rectifier.


Why ?

Arfa
Because there weren't a lot of silicon diodes available in the 1930's?
(I'm just guessing. I wasn't the one who said it.)

On Sat, 2 Nov 2013, Pat wrote:

On Sat, 2 Nov 2013 03:08:45 -0000, "Arfa Daily"
wrote:



"William Sommerwerck" wrote in message
...
Odd, I have one of those in the bathroom, but the *center*
position is off. Probably from the 1930's or 1940's, but I'm
just guessing.

So there are two ON positions and one OFF?

Yes, one of the on positions is dim, the other full bright.
I assume there's a diode in there.

The diode would have to be a selenium rectifier.


Why ?

Arfa
Because there weren't a lot of silicon diodes available in the 1930's?
(I'm just guessing. I wasn't the one who said it.)

I don't think there were many germanium diodes in the thirties, either.

WWII required development of radar, and that meant going higher and higher
in frequency for better resolution. And while they had no problem making
transmitting tubes for the higher frequencies, receiving tubes were an
issue. So they went back to the "cat's whisker" detector, turning that
into a prepackaged germanium diode. And then silicon diodes appeared
after the war at some point.

So unless you wanted a tube rectifier, you had no choice but to use a
selenium rectifier between the point they came into use (I'm not sure
when) and WWII or more likely later. I don't see signs of power solid
state diodes till after the war.

Michael

"Pat" wrote in message
...
On Sat, 2 Nov 2013 03:08:45 -0000, "Arfa Daily"
wrote:



"William Sommerwerck" wrote in message
...
Odd, I have one of those in the bathroom, but the *center*
position is off. Probably from the 1930's or 1940's, but I'm
just guessing.

So there are two ON positions and one OFF?

Yes, one of the on positions is dim, the other full bright.
I assume there's a diode in there.

The diode would have to be a selenium rectifier.


Why ?

Arfa
Because there weren't a lot of silicon diodes available in the 1930's?
(I'm just guessing. I wasn't the one who said it.)


Ah. Ok. I wasn't reading it as actually being of that sort of manufacturing
vintage, in which case, yes, a selenium reccy would probably be the only
solid state possibility. Or maybe copper oxide, do I remember ? Anyways,
whichever, I'm sure even low power examples of those early technology
devices that I remember seeing, would be far to bulky, and run far too hot,
to fit into a wall switch enclosure ??

Arfa

On Sunday, October 27, 2013 8:38:23 AM UTC-5, William Sommerwerck wrote:
I've been selecting parts to upgrade a pair of Advents. In the process, I discovered I didn't know the difference between ON-NONE-ON and ON-OFF-ON. Duh... "We already know the answers -- we just haven't asked the right questions." -- Edwin Land

I remember those old selenium rectifiers, they had a distinct smell if they warmed up during their usage, I remember them being used in car battery chargers in the 1940's.

First solid-state rectifier I remember was a 1N34 that I used in a crystal radio in the 1947-48 time frame.