[GreenKeys] Jack Selection for TTY equipment

[hwhall at compuserve.com]

If interested, I have in my stuff a couple of vintage 1/4 inch teleprinter plugs with red and black colored shells. They came off some old Teletype stuff we played with when I was in college at our college industrial arts department ham station.
 

 Wayne
WB4OGM



-----Original Message-----
From: Roy Morgan <k1lky at earthlink.net>
To: Cory Heisterkamp <coryheisterkamp at gmail.com>
Cc: greenkeys <greenkeys at mailman.qth.net>
Sent: Fri, Nov 15, 2013 5:57 pm
Subject: Re: [GreenKeys] Jack Selection for TTY equipment

  
On Nov 15, 2013, at 7:49 PM, Cory Heisterkamp <coryheisterkamp at gmail.com> wrote:

Evening Greenkeyers,

I wanted to solicit your advice with a project I have in mind. My current TTY arrangement Involves lots of exposed conductors, alligator clips and random wires. I'd like to tidy things up and build my loop supply into an enclosure with ammeter. Seeing as most of my equipment has quarter inch plugs, I'd like to build a series of jacks into the front of the unit to allow me to mix and match equipment. 

I'm wondering, are there certain types of jacks I should be on the lookout for? Won't the traditional style with nut bonded to sleeve create a shock hazard? Your thoughts?


Cory,

I have a strong opinion:


Find and procure a small wooden box that will do all you need.  It’s called the "63 C 1 Telegraph Loop Switchboard" and was used by Western Electric for teletype customers and by the military also.  This little wizard is about 5 inches wide and 8 or 9 inches tall and maybe 4-5 inches from the business panel to the back.  It has 4 rows of jacks: these are labeled LPG1 (looping 1) LPG2 (looping 2), SET, and the fourth is either SET or MISC.  Inside there are terminal points to hook wires to.  The jack types used are type 303A and 438C.  The different jacks accomplish wondrous switching as you plug and unplug the patching cords used with it.  The cords are simple tip-sleeve two conductor cords with 347 plugs on each end (I assume that common phone plugs work fine.)


Basically, with nothing plugged in, the incoming LINE is connected to it’s particular SET.  The box accommodates four LlNES with the four SETs.  The SET might well be a send-receive teletype such as a Model 15.


The LOOPING jacks let you insert another device into the loop - say a Transmitter Distributor, or a tape reader.  The MISC circuit lets you insert into a loop whatever is connected to that jack, such as a loop current meter or maybe a loop supply.


I have puzzled over the various ways this thing can be used, and came to the conclusion that a LOT of equipment can be set up and inter-operated with this apparently simple box.


Note that the jacks used, especially the 438 C jack, does make-before-break and disconnect functions that are needed to prevent opening a loop when you don’t want to.  (You won’t find these jacks at Radio Shack!)  Oh, the panel on this thing is bakelite and it would not do to mount the jacks in a metal panel.


I will attempt to attach a picture of the thing, and won’t be surprised if it does not make it out to the list.  I have pictures of both the box and the circuit diagram from inside one of them.


Roy

Roy Morgan
RoyMorgan at alum.mit.edu
K1LKY Since 1958 - Keep 'em Glowing!






 
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