Author Topic: Now the Story Can be Told - 1949 WECo 500 Set  (Read 237651 times)

Offline Dan/Panther

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Re: Now the Story Can be Told.
« Reply #285 on: March 30, 2010, 01:52:09 PM »
I think the document dated May 1949 allows us to draw the conclusion that the dots were placed on the bezel fairly early in the trial process, perhaps even in 1948. 

D/P has found the next-to-impossible 500, so now it would seem that the truly impossible one would not have the dots.

I must say that after reading the technical information for the equalizer used on the early 500's, I'm wondering if I should be using my 10/50 phone as much as I am.  I'd hate to burn out the equalizer "lamp" on it. 
RP2813, where did you read that about the equalizer. ?
D/P

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Offline Kenny C

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Re: Now the Story Can be Told.
« Reply #286 on: March 30, 2010, 01:57:42 PM »
hey thats my birth day in 1948 ;D
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  Marie B.
1926-2010

Offline rp2813

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Re: Now the Story Can be Told.
« Reply #287 on: March 30, 2010, 03:26:43 PM »
D/P, I read the equalizer info in that same May 1949 document that an earlier post here linked to.  I haven't made it through the entire document yet, but the information about the equalizer filament gave me cause for concern, not only regarding the thing just burning out from use (although I think I read elsewhere that they were designed to last for thousands of hours) but also if the phone itself should take a tumble.  Unless the filament was manufactured along similar lines to a "rough service" light bulb, I'm concerned about its life expectancy but then again, Ma Bell designed and built the 500 with durability in mind and I would like to presume that the equalizer was made to withstand a certain amount of abuse, but I don't know.  I also don't know what sort of equalizer design was incorporated into the 425B network blocks.  Perhaps I'm worried over nothing.

All of this has made me wonder if I should track down a straight handset cord for my 10/50 and take it out of daily use.  It seems a shame to do so, as with vintage cars I've owned, I prefer to drive them rather than keep them under a cheese bell for show only.
Ralph

Offline dencins

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Re: Now the Story Can be Told.
« Reply #288 on: March 30, 2010, 03:33:15 PM »
I think the document dated May 1949 allows us to draw the conclusion that the dots were placed on the bezel fairly early in the trial process, perhaps even in 1948. 

D/P has found the next-to-impossible 500, so now it would seem that the truly impossible one would not have the dots.

I must say that after reading the technical information for the equalizer used on the early 500's, I'm wondering if I should be using my 10/50 phone as much as I am.  I'd hate to burn out the equalizer "lamp" on it. 
RP2813, where did you read that about the equalizer. ?
D/P

http://www.telephonecollectors.org/DocumentLibrary/WesternElectric/500-Set-Design-1949.pdf

Starting on page 91.

Dennis

Offline Dan/Panther

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Re: Now the Story Can be Told.
« Reply #289 on: March 30, 2010, 03:48:17 PM »
RP;
Being that the phone was not a user owned item, I would think they would have made the equalizer to last as long as the expected lifespan of the phone, as the subscriber would not be responsible for repairs, why would the company manufacture an item they would have to pay a service tech to constantly change. Mine appears to have resistance and continuity through the terminals as per my multimeter. And I'm quite certain no great care has been taken in the handling and storage of my phone which predates 1950 by I hope at least one year. the article state the EQ was rated at 3000 use hours. That's not as long as it sounds.

If you go by an average cell phone program of 1000 minutes a month. Then calculate it out. That's calculated over a projected 3000 hours useful lifespan, that's 180,000 minutes at 1000 minutes a month, that's 15 years, if you use it an average of 33 minutes a day. I wouldn't worry.
D/P
« Last Edit: March 30, 2010, 03:51:41 PM by Dan/Panther »

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Offline Phonesrfun

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Re: Now the Story Can be Told.
« Reply #290 on: March 30, 2010, 03:56:19 PM »
The 1949 write-up quoted a 3,000 hour lifespan based on the new equalizer having a filament in it.  (The 425 B and later networks eliminated the filament-based equalizer, and replaced it with varistors).

Anyway, the 3,000 hour lifespan quote was based on their estimate that the filament should have about the same life as the average switchboard lamp.  I don't think at that time they really had much in the line of experience to really know how long it would last.

-Bill G

Offline rp2813

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Re: Now the Story Can be Told.
« Reply #291 on: March 30, 2010, 04:16:36 PM »
I'm tending to lean toward the assumption that AT&T wanted everything over-engineered for exactly the reasons D/P stated re: the equalizer.  It could very well be that their estimate of 3000 hours could be way below the actual life span. 

I'll take D/P's advice and not worry about it.  My 10/50 usage averages out to only a few minutes per day.

I'm still not clear on how the equalizer works, though.  Let's say I'm calling my next door neighbor.  What's the equalizer doing as compared to calling someone across town who is served by a different switch?  Keep in mind that I am at the very edge of my switching office's reach.  Would things be different if I lived across the street from the switch?  Is there an easy way to explain this to us challenged masses?
Ralph

Offline JorgeAmely

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Re: Now the Story Can be Told.
« Reply #292 on: March 30, 2010, 04:28:58 PM »
Ralph:

If you are far away from the central office, the current through the filament will be small, thus lengthening the life of the equalizer. I would keep using it as you do today.
Jorge

Offline Dan/Panther

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Re: Now the Story Can be Told.
« Reply #293 on: March 30, 2010, 04:30:29 PM »
Apparently it reads the line resistance and adjust accordingly so a close call is not over modulated, like the article says; "to the point that the caller and the called could not stand the loudness"
D/P

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Offline Phonesrfun

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Re: Now the Story Can be Told.
« Reply #294 on: March 30, 2010, 05:14:51 PM »
RP:

The equalizer is kind of a volume control that bases its setting on the current it senses.  The current is a direct function of how far away you are from the central office, which is where your phone is connected to at the other end.  If you are 5 miles from the CO, then that is your loop distance, because that is where the central office battery that supplies the current is.  It doesn't matter whether you are calling accross the street, or across the country or to the Moon.  Your loop distance is the distance to the central office.

But lets say you work in an office that has a PBX that is 5 miles from the central office.  A PBX supplies its own battery supply for that system.  Any calls within the PBX are very short loops; maybe only tens of feet.  However, once you dial a 9 for the outside line the PBX switches your call over to the telephone company central office.  Now suddenly, the loop length turns from, say 100 feet to 5 miles.  The equalizer in the phone makes the needed adjustments to compensate for that and opens the volume wide open, and you will notice very little change.

A non-equalized phone like a 302 and earlier could have a very noticeable difference between long and short loops.  In a 302 environment, the local PBX could sound too loud, and a call through the central office could be annoyingly weak.

The equalizer was a giant step for the phone company.
-Bill G

Offline McHeath

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Re: Now the Story Can be Told.
« Reply #295 on: March 30, 2010, 05:23:08 PM »
Welcome to the forum Paul.

Quote
We still need to find a known 1949 set to compare with yours and a 1950 set to fill in the gaps.

Are there any known 1949 sets?

Do you believe that this chassis of D/Ps is a 1948 field trial unit?



Offline bwanna

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Re: Now the Story Can be Told.
« Reply #296 on: March 30, 2010, 06:04:47 PM »
we are getting a little off the topic of dan's amazing find. but to the subject of equalizers i would like to add that loads coils are installed in the plant now. simply put these are amplifiers placed at 6k intervals on loops >18k.
not sure when these came into use. but load coils ensure signal is as strong 8 miles away from the CO as it would be next door to the CO. so i am thinking once load coils were in use, the equalizer was no longer necessary ??? also due to this amplification, i think a 302 would sound just fine regardless of loop length.

http://tinyurl.com/ygq39yf

ps. bill g started another thread on this particular topic

http://www.classicrotaryphones.com/forum/index.php?topic=2430.0
« Last Edit: March 30, 2010, 06:41:03 PM by bwanna »
donna

Offline Jim S.

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Re: Now the Story Can be Told.
« Reply #297 on: March 30, 2010, 06:20:57 PM »
Here is the 12/49 Life magazine article. Some photos are in the Life archive, However it does have a photo that shows a riveted foot.

http://books.google.com/books?id=VUEEAAAAMBAJ&pg=PA67&source=gbs_toc_r&cad=1#v=onepage&q=&f=false


Jim
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Offline dencins

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Re: Now the Story Can be Told.
« Reply #298 on: March 30, 2010, 07:21:33 PM »
Here is the 12/49 Life magazine article. Some photos are in the Life archive, However it does have a photo that shows a riveted foot.

http://books.google.com/books?id=VUEEAAAAMBAJ&pg=PA67&source=gbs_toc_r&cad=1#v=onepage&q=&f=false


Jim

So far I have seen the following changes from field trial version to production.

1.  Footpads from screwed on to riveted changing the footpad and base plate tooling.

2.  The dial bezel changed from some type of molding process to painted on.

3.  The plungers changed from clear, flat top to black, rounded top.

4.  Dots added to the dial plate during the field trial.

5.  Plunger levers from horizontal to vertical
 
6.  Ringer mounting method(?) to something(?)

Were there other changes?

Dennis

Offline McHeath

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Re: Now the Story Can be Told.
« Reply #299 on: March 30, 2010, 07:31:25 PM »
As far an what use an equalizer has on modern lines I don't know.  I do know that my 1951 J/K model 500, which has the 425A network and no equalizer, has annoyingly loud sidetone.  So annoying that I put a resistor on the terminal block to reduce it to tolerable levels, and now the phone is quite pleasant to use. 

But I don't know if this was a problem with having the 425A network and no equalizer.

Really nice that Paul put the blueprints up for the 500 series on his site, and they are just like the phone that D/P has!