[GreenKeys] M19 Current Loop Testing

[Joe Duszyński]

If you want to "just receive RTTY/ITTY" a unit like the suggested TU-170,
or Info-tech M-100,M-200,M-600 ect or a HAL that also controls the motor
(autostart) would be easiest. You can always add the computer. optocoupler
rs-232 interface, inline at a later time.
Most of those RTTY boxes generate the loop current for you and can usually
drive 2(sometimes more) teletypes. Some like the HAL's can be wired to use
an external supply......

The units that supply the loop current and voltage from a USB port are less
flexible you can't for instance run a couple machines from its loop they
are designed with one set of coils in mind.

You can also make your own loop supply... 120VDC and a 2000 ohm resistor
gets you 60ma.

Your M-19 table should have the rectifer/loop already in it.





On Thu, Mar 17, 2022 at 8:38 PM steve bennett via GreenKeys <
greenkeys at mailman.qth.net> wrote:

> Try one of these if you can find one.
> It's a RTTY modem. It will take audio from iTTY and produce the current
> loop signals.
>
> https://www.w6iwi.org/rtty/tu170/
>
> -Steve
>
> On Thursday, March 17, 2022, 08:23:26 PM EDT, Matthew Wagner <
> mattwagner92597 at gmail.com> wrote:
>
>
> Hi all,
>
> I'm relatively new here, but I've been working on my first restoration (an
> M19) and I'm pretty close to having it done. The only thing left to test
> out is the actual Tx/Rx loop circuits.
>
> I'm not entirely sure where to start out looking for something to
> interface with the 60mA loop. Preferably RS232 or USB to make things
> easier. I want to eventually get it up on ITTY once everything's working
> properly.
>
> If anyone has some pointers on some gear to start looking for, I'd
> appreciate some direction.
>
> Much Appreciated,
> Matt Wagner
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