[GreenKeys] Jack Selection for TTY equipment

[WA5CAB at cs.com]

OK.  With that plus some jacks not in the series string but each connected 
to a device you had the equivalent of one loop plus the bottom row of one of 
the military patch panels.  I just remembered that the panel I had (have?) 
was a TT-23/SG.  The one that I can't recall is the more common later higher 
numbered smaller one.  I have a reprint available of the NAVSHIPS manual on 
TT-23B/SG.

The TT-23 had six columns and four rows of jacks, plus an on-off switch and 
a rheostat at the top of each column.  And a MA meter with a 6-position 
loop selector switch.  In each column (loop), Jacks 1, 2 and 4 were shorting.  
Jack 3 was what I think was called Normalling.  A device (usually a machine) 
was hardwired to it.  If you plugged a patch cord into Jack 1 or 2, you got 
the loop on the other end.  If you plugged a patch cord into Jack three, 
instead of the loop you got the device and the loop was opened.  The jacks in 
Row 4 were shorting but weren't in the loop.  Instead, they were hardwired 
to external devices (or into a loop on another patch panel),  SOP was to wire 
the panel(s) if possible) such that most of the time, no patch cords were 
needed.

The jacks and plugs were 2-circuit.  The plugs looked just like standard 
PL-55, 49109 or NAF 1136-1, but may not have been.  I never noiticed.  The way 
in which these panels mostly got around the shock hazard was that the 
sleeve connection was made by a second insulated spring finger contact instead of 
by the jack panel mounting threaded part.  

The only way in which you might get shocked would be if you touched the 
plug sleeve while the plug was only partially inserted.  As someone earlier 
pointed out, 1/4" stereo jacks would eliminate even this.  But I do not know 
for certain whether the ring on the stereo plug is in the correct longitudinal 
location to work with the sleeve contact on the military panel jacks.  I 
had a number of original patch cords and never checked it.

In a message dated 11/16/2013 10:55:47 AM Central Standard Time, 
rmowery28146 at earthlink.net writes: 
> At one time I had an aluminum box with a milliamp meter and loop supply I 
> built in it.  I cut out part of it and put in a piece of plastic and 
> mounted 6 of the 1/4 inch phone jacks.  They were closed circuits except for 
> one.  I left that one as an open circuit jack so I could unplug from it and it 
> would open the loop.  The plastic was to insulate the jacks.  The jacks 
> were at the lowest or grounded part of the loop.  While it did not prevent a 
> total shock, it would be onthe lower voltage part.  Also the tip of the 
> jack was set up to be the most positive part of the circuit.
>  While not totally safe, it was the best I could come up with at the time 
> with what I had to work with.
> 
>  
> >> ----- Original Message ----- 
>> From: WA5CAB at cs.com 
>> To: greenkeys at mailman.qth.net 
>> Sent: Saturday, November 16, 2013 11:25 AM
>>  Subject: Re: [GreenKeys] Jack Selection for TTY equipment
>>  
>> 
>> The problems with using dumb (i.e., with no switches) jacks are:
>> 
>> 1) The only way in which you can jack two or more machines in series is 
>> by using shorting plugs for when you don't want them in series.
>> 
>> 2) If you do it that way, everything runs open while you are getting it 
>> set up.
>> 
>> 3) If you have a machine, convertor or exciter normally wired into a 
>> loop, you can't take it out of that loop and patch into another one either 
>> with or without disturbing its default loop.
>> 
>> You will be much better off if you locate and acquire something like a 
>> TT-23 TTY Panel.  I can't at the moment recall the nomenclature of the 
>> earlier one that I actually used for a few years.  looked like an overgrown 
>> TT-23.
>> 
> 
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