[GreenKeys] de K8WXQ HAL ST-8000 TU HelloRS-232 to Teletype 60mA LOOP Circuit

[Pete G]

Hi Al,

The circuit I used for my ST-8000 can be found on this page. The design
worked very well.
https://www.aetherltd.com/connecting.html
The design worked very well.

For the solid state relay, I used a VOR2121A8 as the specified HSR312L
relays are obsolete.

Pete

[image: Slide1.JPG]


On Tue, Feb 24, 2026 at 9:05 AM Al K8WXQ via GreenKeys <
greenkeys at mailman.qth.net> wrote:

> Hello  2/24/2026
> I am getting ready to run a Model 28ASR Teletype. It has not arrived yet,
> so I do not know its requirements? I wonder if there as a circuit I can
> fabricate to connect the HAL ST-8000 (Not A) with RS-232 to drive a  60 or
> 20 mA Teletype LOOP using a 120VDC Power Supply.  Presently, I am looking
> at the isolated output Circuit for a HAL DS-3100 Terminal with
> Opto-Isolators (4N35) for TX and RX.  Anyone out there in Teletype Land
> have any experience connecting RS232 to a Teletype LOOP???  Are there any
> ready to go units available for this task?
> Thank you so much. Al K8WXQ.
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