Author Topic: 302 phone -- What does this do?  (Read 697 times)

Offline novarlynx

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302 phone -- What does this do?
« on: July 24, 2016, 01:23:40 AM »
A friend who knows I collect phones gave me a metal housing WE 302 from 1938.

Inside it, I found this rectangle shaped thing next to the dial. It says "WESTERN ELECTRIC MADE IN USA" and "10-38" but other than that I cant tell what it does. There's some wires coming out of it, two going to the dial and looks like one going to the hook switch.

I have two plastic 302s from 1948 and 1947 and neither of them contain the mystery component.

Thanks for the help!
The digital PSTN is so boring now. I wish I could have experienced what it was like to use the Bell System with all its analog wonders.

Well, at least we have museums. Right?

Offline Kenton K

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Re: 302 phone -- What does this do?
« Reply #1 on: July 24, 2016, 01:46:58 AM »
This is a dial filter that stops the dial pulses from interfering with I believe AM radio signals. This is was an optional. If you look in most wiring diagrams, you can see the filter wired in drawn dashed wires. I think the 500 set had the filter built into the network, but it's been a while since I've looked at a schematic so could be wrong.

Ken

Offline TelePlay

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Re: 302 phone -- What does this do?
« Reply #2 on: July 24, 2016, 08:55:54 AM »
It's a 61A filter



and it's been discussed in several other places on the forum over the years. This topic is a good discussion, with pictures, of the filter

http://www.classicrotaryphones.com/forum/index.php?topic=12818.0



including the definitive explanation plus wiring diagram provided by unbeldi

http://www.classicrotaryphones.com/forum/index.php?topic=12818.msg134690#msg134690


            John . . .

              

Offline kb3pxr

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Re: 302 phone -- What does this do?
« Reply #3 on: January 26, 2018, 07:02:37 PM »
The dial filter performs several functions. First, it prevents radio frequency interference as already mentioned, secondly it prevents interference to other customers. Third and most important, it protects the dial pulse contacts in the dial by preventing the line inductance from generating a nasty arc on the dial contacts which could weld them closed.