Potentiometer/Rheostat/Whatever

[genek]

WRT to the occaisionally reoccurring discussion of what these buggers are, I fired up the patent research database and entered "aetna pollak," and out popped the patents.

The official name on the documents is "Control Rheostat." The patents are dated 1940.

[Zilch]

Read the patents. They are for a different device:

This invention relates to a control rheostat structure, and more particularly to such a rheostat structure which is used for controlling electrically-operated accessory elements in an automobile.

Structurallly, the AR "pot" is a wirewound potentiometer.

Electrically, it is employed as a rheostat in AR2, and as a potentiometer in other models....

[genek]

Read the patents. They are for a different device:

Structurallly, the AR "pot" is a wirewound potentiometer.

Electrically, it is employed as a rheostat in AR2, and as a potentiometer in other models....

I found six different patents, only two of which (the wrong ones)

are downloadable for free. But they're all titled the same. Of course,

being filed in the 1940's by a company whose main line of business

was motors, how they ended up being used in AR speakers has no

bearing on what the manufacturer called them. It does, however,

explain why I've never been able to turn up any information with

a search for "aetna pollak potentiometer."

[Zilch]

I found six different patents, only two of which (the wrong ones)

are downloadable for free.

Post the patent numbers, please.

Fact is, an inventor may use whatever words he wants, so long as they are defined by the disclosure, and their meaning is clear.

From an engineering perspective, the use matters. A potentiometer may be configured as a rheostat using the wiper and one end of the resistance element. Typically, the other end is also connected to the wiper.

Schematically the symbols are different. A rheostat is a two-terminal variable resistor, whereas a potentiometer is a variable resistance divider, a three-terminal device.

http://www.allaboutcircuits.com/vol_6/chpt_3/7.html

[genek]

Post the patent numbers, please.

Fact is, an inventor may use whatever words he wants, so long as they are defined by the disclosure, and their meaning is clear.

From an engineering perspective, the use matters. A potentiometer may be configured as a rheostat using the wiper and one end of the resistance element. Typically, the other end is also connected to the wiper.

Schematically the symbols are different. A rheostat is a two-terminal variable resistor, whereas a potentiometer is a variable resistance divider, a three-terminal device.

http://www.allaboutcircuits.com/vol_6/chpt_3/7.html

By the definition in your website, just about every product I can find that is sold as a rheostat is a potentiometer. Since I've heard at least three or four totally conflicting "differences between" a rheostat and a potentiometer over the years and am not an electrical engineer (if it weren't for the wire color notations on the schematics in CSP I'd be SOL as far as changing an electronic part is concerned), all I know is what manufacturers put on their boxes and datasheets. If a company says its product is a rheostat, then you can post all the websites you want, but as far as I'm concerned it's whatever I have to call it to order one or find info on it. Sorry if that's not good enough.

I should have written the patent numbers down, but all I was looking for was listings with the company name on them and their titles. If I can persuade our keeper of the patent database account at work to let me play in it again on Monday, I'll try to get them, or better yet a pdf of the one I thought was the closest to AR's. Nothing was a perfect match, but I don't think companies file for patents on every model they make, just the ones where they introduce something new.

[Zilch]

By the definition in your website, just about every product I can find that is sold as a rheostat is a potentiometer.

I recall reading here that one of those actually WAS a two-terminal rheostat, and the "ABORT" sign went up real quick....

This website has become an amazing example of finest quality information.

Well, we're workin' on it....

http://en.wikipedia.org/wiki/Rheostat#Rheostats

Scroll up for what a potentiometer is....

[genek]

I recall reading here that one of those actually WAS a two-terminal rheostat, and the "ABORT" sign went up real quick....

Well, we're workin' on it....

http://en.wikipedia.org/wiki/Rheostat#Rheostats

Scroll up for what a potentiometer is....

The big problem with wikipedia is that anybody can say anything, and it sits there until prople who know better fix it. I prefer a more authoritative source, like the IEEE. This is all I could find on their site:

"Device number 70 - rheostat A device used to vary the resistance in an electric circuit when the device is electrically operated or has other electrical accessories, such as auxiliary, position, or limit switches."

From IEEE C37.2-1996. The full standard requires a paid membership to access, but here you can view a survey taken for a proposed revision of the standard that quotes the definition:

http://grouper.ieee.org/groups/sub/wgc5/do...al%20Report.doc

There doesn't seem to be a similar IEEE device listing for potentiometer.

Ultimately, as long as we all agree that the bottom line goal is to make our speakers perform the way we want them to, we could all just agree to just call these "Steve" here and I'd be content.

[Zilch]

The big problem with wikipedia is that anybody can say anything, and it sits there until prople who know better fix it.

Wikipedia used to be wrong, also. It was corrected by someone knowledegable ~12/07.

Check the revision history and discussion. The earlier version was dubbed "Ignorant."

[Zilch]

I prefer a more authoritative source, like the IEEE.

Wikipedia's reference:

The Authoritative Dictionary of IEEE Standards Terms (IEEE 100), seventh edition, Piscataway, New Jersey: IEEE Press. ISBN 0-7381-2601-2.

There's a bunch of interesting links at the bottom of the page, as well....

[genek]

Wikipedia's reference:

The Authoritative Dictionary of IEEE Standards Terms (IEEE 100), seventh edition, Piscataway, New Jersey: IEEE Press. ISBN 0-7381-2601-2.

There's a bunch of interesting links at the bottom of the page, as well....

I think our EE at work is active in the IEEE. Just for laughs, I'll see what he says the difference is between a rheostat and a potentiometer.

[genek]

It turns out that our patent database account only displays the first page of the patent with all but the first 3 digits of the patent number blanked out (I didn't notice this last week because I was only looking at names and pictures) and is locked against printing. To view, print or download a full patent with no blank outs is an additional fee.

So this is all I can get for free:

Six patents.

Four beginning with 220.

One beginning with 221.

One beginning with 223.

All date from between 1940-1948.

All are titled "Control Rheostat."

All have three terminals.

The one that looks most like the AR controls is one of the 220's. Its picture differs from the units we see in ARs in that it has a knob rather than a shaft with pointer, screw terminals instead of solder, and the width/depth looks rather fatter and/or flatter, but the scheme of the winding on a ceramic back piece and the wiper spring-loaded against it from the front housing (which I don't think I've seen on anybody else's rheostat or potentiometer) is pretty much the same as the ones I have disassembled on my desk right now.

And here's what our in-house EE told me...

"Once upon a time," "rheostat" was the generic term for all types of variable resistor. A "potentiometer" was a "rheostat" with the required terminals to enable it to act as a voltage divider. The 1940's Aetna-Pollak patent titles would have been based on that convention, so either name would have been appropriate, and a company whose main business was motors would have labled every such device they made as a "rheostat."

Virtually all variable resistors are now manufactured with voltage divider terminals. Some customers call the ones they buy "rheostats," and others call theirs "potentiometers," and product names are just what the majority of the intended customers prefer. He says he's seen identical products listed as "rheostats" by electrical suppliers and as "potentiometers" by electronics suppliers.

In current terminology (IOW, according to IEEE), the correct term to describe the device should now be "variable resistor," and "rheostat" and "potentiometer" should only be employed to describe how the "variable resistor" is being used.

He says it's probably been 20 years since he last used anything new labeled "rheostat" that only had two terminals.

[Zilch]

In current terminology (IOW, according to IEEE), the correct term to describe the device should now be "variable resistor," and "rheostat" and "potentiometer" should only be employed to describe how the "variable resistor" is being used.

COOL! You've sussed it out.

We don't have to call them "Steve," after all....

[kkantor]

Hi. All US patents, and even patent applications, are public domain by law. You can search and download them (as PDF's) at www.google.com/patents, as well as other places. They always have a rotating selection of funny patents on that page, too. Each time you refresh your browser, you will get more. I love them!

According to the esteemed electrical engineer, Dr. Lana Titveneer, "rheostat" is an archaic term. It is possible to build a crossover with rheostats, chokes and condensers, but it would sound pretty vintage.

-k

www.kenkantor.com

www.ztamplifiers.com

[genek]

Hi. All US patents, and even patent applications, are public domain by law. You can search and download them (as PDF's) at www.google.com/patents, as well as other places.

And yet, amazingly, companies like the one I work for will pay for patent searches, and those paid searches will almost always find patents that the free searches do not. Must be a testament to the incompleteness of the paper/microfilm-to-digital tranfer of old govt files and the snail-like speed with which new data is uploaded.

Just for laughs, I entered our company name into the google patent search engine and got two. I know we have at least a half dozen either issued or pending.

[kkantor]

And yet, amazingly, companies like the one I work for will pay for patent searches, and those paid searches will almost always find patents that the free searches do not. Must be a testament to the incompleteness of the paper/microfilm-to-digital tranfer of old govt files and the snail-like speed with which new data is uploaded.

Just for laughs, I entered our company name into the google patent search engine and got two. I know we have at least a half dozen either issued or pending.

I do patent searches as a big part of my living. I was working as an "expert" on big audio technology IP cases, and have also been the gatekeeper of IP for various companies I was CTO for. For years, my personal choice was Delphion, due to its ability to easily set up court presentations and trace reference trees, EP and WIPO, so I understand the benefits of a pay-for-play search company. But I find that I can do most of what I need these days between Google, USPTO, and various applications designed to mine the USPTO data. Curious which patent search company your firm uses, Derwent?

-k

[Pete B]

Funny ... IBM had an early patent search server that I often used years ago. When we mentioned it to our legal department they said don't use it, since they certainly monitor it to see what competitors are looking at.

[Zilch]

According to the esteemed electrical engineer, Dr. Lana Titveneer, "rheostat" is an archaic term. It is possible to build a crossover with rheostats, chokes and condensers, but it would sound pretty vintage.

Heads UP, CSPers, Ken has inadvertently revealed the enlightened path to Vintage Sound....

[genek]

I do patent searches as a big part of my living. I was working as an "expert" on big audio technology IP cases, and have also been the gatekeeper of IP for various companies I was CTO for. For years, my personal choice was Delphion, due to its ability to easily set up court presentations and trace reference trees, EP and WIPO, so I understand the benefits of a pay-for-play search company. But I find that I can do most of what I need these days between Google, USPTO, and various applications designed to mine the USPTO data. Curious which patent search company your firm uses, Derwent?

-k

The database lives on someone else's system and she logs onto it for us. I think from the splash screen that comes up on login it's a division of Reuters.

I just surfed over to USPTO, and its search didn't even turn up the two Aetna-Pollak patents that Google and FreePatentsOnline finds.

BTW, Ken, when you were at AR, what did the folks out on the factory floor call those level controls...?

[genek]

Heads UP, CSPers, Ken has inadvertently revealed the enlightened path to Vintage Sound....

I suspect that many of us who are old enough to remember when it was common to call these rheostats are already about as vintage as we can stand to be...

[kkantor]

Funny ... IBM had an early patent search server that I often used years ago. When we mentioned it to our legal department they said don't use it, since they certainly monitor it to see what competitors are looking at.

Of course there are questions about the data collection of usage. Most pay databases have subscriber agreements to minimize the exposure, but it is there. More significantly, if one loses a patent infringement case, the court-ordered damages are usually much higher if it can be proved that the infringer was aware of the relevant patent(s). Thus, in-house legal departments are sometimes hesitant to leave a paper trail.

Anyway, I am far from an expert in patent law. I just did what they told me! "Go find out if anyone has patented speakers made from mashed potatos." "Are Newton's 12th claim about stereo imaging and Leibnitz's 6th claim concerning soundstage really equivalent, and did Al-Tusi predict them both?"

More interestingly, it was often an assignment to figure out how to explain arcane matters to a jury. "Can you sketch a cartoon stick figure to illustrate temporal unmasking across adjacent critical bands?"

-k

[kkantor]

The database lives on someone else's system and she logs onto it for us. I think from the splash screen that comes up on login it's a division of Reuters.

I just surfed over to USPTO, and its search didn't even turn up the two Aetna-Pollak patents that Google and FreePatentsOnline finds.

BTW, Ken, when you were at AR, what did the folks out on the factory floor call those level controls...?

They called them, "Level Controls." No joke.

I'd have to look at the library to be sure, but I suspect that the technical documentation, bills of materials, etc, mostly referred to them in whatever way they were listed in the supplier's catalog.

Thus, on a parts list or assembly print, one might see a line item:

XXX-XXX-XXXXXXXX Level Control, 20 Ohms. Aetna-Pollack #123ABC-Q.

That sort of thing. When you looked on the actual detail print referenced by the XXX part number, you would see whatever electrical, mechanical and cosmetic specs the engineers thought should be documented. There might even be a second-source listed on the detail print:

XXX-XXX-XXXXXXXX Level Control, 20 Ohms. Imin Controls, Inc. #23422-66H-002.

-k

[kkantor]

And yet, amazingly, companies like the one I work for will pay for patent searches, and those paid searches will almost always find patents that the free searches do not. Must be a testament to the incompleteness of the paper/microfilm-to-digital tranfer of old govt files and the snail-like speed with which new data is uploaded.

Just for laughs, I entered our company name into the google patent search engine and got two. I know we have at least a half dozen either issued or pending.

I'm pretty sure the Google patent search is as complete as any other. As far as I know, they are all just front ends to the USPTO database. If you found something with one, and not the other, which is not uncommon, it has to do with refining your search fields and boolean logic. For example, several databases will not return non-explicit queries for the patent assignee, so putting in a company name will yield nothing, unless you go to Advanced Search and specify the Assignee field. For me, at least, patent searching is hard, and takes a long time.

-k

[genek]

I'm pretty sure the Google patent search is as complete as any other. As far as I know, they are all just front ends to the USPTO database. If you found something with one, and not the other, which is not uncommon, it has to do with refining your search fields and boolean logic. For example, several databases will not return non-explicit queries for the patent assignee, so putting in a company name will yield nothing, unless you go to Advanced Search and specify the Assignee field. For me, at least, patent searching is hard, and takes a long time.

I'm sure it must be for us, too, or management would be telling us all to go google for patents.