[GreenKeys] Fwd: Is this part this?

[Duncan Brown]

Windows XD,

The circled item on the schematic is a polar relay and it plugged into 
the socket in your picture.  The polar relay was the opto-coupler of the 
1930s.  It isolated the machine's loop from the line.

When these machines were originally developed (in the 1900-1930s) they 
were used on telegraph lines that could be 20 miles (or more) long.  
Teletype Corp. used the generic term "Printing Telegraph" for their 
equipment up into the 1950s.

Since our TTY loops are measured in feet, not miles, we don't need the 
polar "Line Relay" option any more (though a lot of the M28 equipment 
still used them).

We generally just wire the selector magnets in series with the keyboard 
into our local 60 ma current loop, which is generally supplied by the 
modem/Terminal Unit/FSK Converter.  just make sure that the loop is 
limited to 60 ma before connecting it to the M19!

So you can just bypass and forget about the polar Line Relay.

Good luck & Have fun,

Duncan
K2OEQ







-------- Forwarded Message --------
Subject: 	Re: [GreenKeys] Is this part this?
Date: 	Mon, 28 Jul 2025 11:02:27 -0400
From: 	Windows XD <antech6586856 at gmail.com>
To: 	Duncan Brown <duncanancy at earthlink.net>



Apologies, it's a model 19, the photos should be attached to this post.

On Mon, Jul 28, 2025, 9:20 AM Duncan Brown <duncanancy at earthlink.net> wrote:

    What model TTY??

    On 7/28/2025 8:54 AM, John, W9DDD wrote:
>     Was there supposed to be attachments or a link?
>
>
>     On 7/27/2025 11:07 PM, Windows XD wrote:
>>     Dear all,
>>
>>     I'm finally getting back to my teletype project, and mine seems
>>     all miswired. Is the circled part on the schematic the same part
>>     that's circled in the photo?
>>
>>     P.S. What is it? Is it something kind of transformer?
>>
>>     All help is appreciated!!
>>
>>
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     >>> Jordan Spencer Cunningham's GreenKeys Search Tool:
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     >>> 2002-to-present greenkeys archive:
    http://mailman.qth.net/pipermail/greenkeys/
     >>> 1998-to-2001 greenkeys archive:
    http://mailman.qth.net/archive/greenkeys/greenkeys.html
     >>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
    http://comcents.com/tty/greenkeyssearch.html

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