[GreenKeys] TTY loop jack boxes - SET, LPG, MISC

Mon Aug 16 04:42:44 EDT 2021

Ah, hmm.  I hadn’t thought of that.  Another point to consider :->.  Thank you.

From: John W9DDD [mailto:w9ddd at tapr.org] 
Sent: Sunday, August 15, 2021 7:59 AM
To: Paul Birkel
Cc: Nick England; Greenkeys
Subject: Re: [GreenKeys] TTY loop jack boxes - SET, LPG, MISC

GM Paul,

One comment,  I think you'd want a ROTR or other receive device connected as a SET on a separate channel rather than MISC so that it won't run open when turned on.  Then a TD connected as a MISC could be patched to one channel to print on the 15 or the other to make a tape copy.

Pardon my rambling.  My crayon is pretty blunt this early in the morning.

John, W9DDD

On Aug 15, 2021, at 5:21 AM, Paul Birkel <pbirkel at gmail.com> wrote:

So … I’m still not the “sharpest crayon in the box” on this topic.  Let me use the SB-1203/UG as my example (documented online at: https://www.navy-radio.com/rtty/sb1203.htm).  It has six identical circuits (“channels”) – one example diagrammed at:  https://www.navy-radio.com/rtty/patch/1203a-man-07.JPG

Inside the unit there are several sets of terminal strips (see: https://www.navy-radio.com/rtty/patch/1203a-man-01.JPG) establishing pairs of permanent connections corresponding to the TB-* appearing at the bottom of the example schematic diagram.

TB-101 would normally connect to some equipment  (this is, I think, “(LINE LPG)” in the terminal strip diagram) that is _always_ in that particular channel (examples from that terminal strip diagram are “RADIO ADAPTERS, FREQUENCY SHIFT KEYERS, LINE MODULATORS”), and may optionally supply loop-current, correct?

Alternatively TB-101 could be strapped closed under the assumption that there is a SET connected to TB-102 and there is a loop-supply established via TB-104 and the default strapping?

The distinction between TB-101 and TB-102 seems to be whether the SET supplies loop-current or not, correct?

TB-102 (SET jack) would connect to some equipment that is normally in that channel, but can be either:

    (1) removed from that channel by inserting some sort of “dummy” plug (has no internal wiring)? … or

    (2) removed from that channel and connected into some other channel using a patch cord

            that establishes a connection between two plugs where the second plug is then inserted into

            a LPG jack on another channel?

TB-103 (MISC jack) would connect some equipment that is not in any channel, to some channel using a patch cord  to a LPG jack?

(The documentation for this unit is quite good; my comments above attempt to summarize my functional understanding of how it is intended to be employed as an exemplar of what I assume is a pretty standard approach to loop jack boxes.)

Is “patch cord” the correct terminology?  Is it just wired tip-to-tip and ring-to-ring (or shell-to-shell if two-wire)?  Are they normally TRS (shell left unconnected?) or TS?

Now, for a use-case, if my source were a self-powered loop from a Flesher TU-170 (which incorporates a loop supply and 0.125A fuse) it seems to me that I’d:

1.      Strap the SB-1203/UG for REMOTE internally (rather than use the default strapping for a TB-104-connected loop supply).

2.      Connect the TU-170 to TB-101.

3.      Connect a (for example) M15 to TB-102 (SET jack).

4.      Connect a (for example) M14 ROTR to TB-103 (MISC jack).

5.      Connect a (for example) M14 TD to a different TB-103 (some other MISC jack)

6.      Optionally add a loop-cable from MISC to an JPG jack to use the M14 ROTR to generate a paper tape of traffic between the TU-170 and M15.

7.      Optionally add a loop-cable from other-MISC to an JPG jack to use the M14 TD to read a paper tape “into” traffic between the TU-170 and M15.

8.      Optionally add a loop-cable from SET to an JPG jack in some _other_ channel to move the M15 to that other channel (which would need to have at least loop supply established).

Would this be a reasonable approach?  Would it be a _good_ approach if these were the four items to be co-employed in this use-case :->?

Would it, in fact, be better to treat the M14 TD as a SET in a different (powered) loop in which case I could then either:

A.    cross-connect the M15 there, or

B.     cross-connect the M14 ROTR there, or

C.     cross-connect the M14 TD into the TU-170 loop?

This seems like a more flexible approach assuming that there is available a separate loop supply for the second loop.

Am I thinking about all of this “right”?  Inquiring minds want to know!

Thank you,

paul

(A long message, but I’ve not gleaned enough specificity from GK traffic archives.  Hopefully by being pedantic here … we’ll avoid more “dull crayons” in the future :->)

From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Nick England
Sent: Sunday, August 08, 2021 3:33 PM
To: Greenkeys
Subject: [GreenKeys] Fwd: TTY loop jack boxes - eBay

Argghh - I forgot to include the link to my page with schematic and explanation

https://www.navy-radio.com/rtty-patch.htm

In the schematic for this type of box, you will see that the LPG jacks are shorted when nothing is plugged in. When nothing is plugged into the SET jack, the associated equipment is in the loop. When you plug a cable into into the SET jack, the equipment is taken out of the loop onto the cable and the loop is shorted. This is so you can plug the equipment normally in Loop 1 into Loop 2 for example and vice-versa (jumper SET-1 to LPG-2 and jumper SET-2 to LPG-1).

"NOTE: Anyone patching or unpatching circuits from a TTY panel must be sure to pull the plug from the looping jack (LPG) before removing the other plug from the SET (machine) jack. Pulling the SET jack first interrupts all TTY message traffic on that channel. IT ALSO PRODUCES A DANGEROUS DC VOLTAGE ON THE EXPOSED PLUG!" 

Nick England K4NYW
www.navy-radio.com

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