I use small 1:1 isolation transformers (from my junkbox) for 3 of my main loops and for a local test loop in the cellar where I work on my model 15, 14 and 28 TD'S  and 28 ROTR's . That gives me about 180 volts. I start with a 2K, 10 Watt resistor then a 15K wirewound pot to set the current.

I have also built a loop supply with a 56 Volt transformer from eBay which gives me about 80 Volts. I use that for my Robot keyboard or my MFJ -1224 so I don't stress the keying transistors too much. I will be building at least one more of those.

The 4th main loop is connected directly to a Dovetron, which I used to use for testing teletypes with ITTY news until I got disgusted with them.

I now have my own news feed, mainly articles for newsforkids.net - it loops every two hours but it is better than lengthy articles by people pushing personal agendas, lengthy weather reports for who knows where in the world and lengthy farming reports. (Really, how many farmers have teletypes?) In my opinion, ITTY news has become a waste of paper and ink. I gave up on autostart months ago when, instead of "Today in History" which I enjoyed reading every morning, I found a marine weather forecast for the New York area - more waste of paper and ink.

I have a second test channel of my own running foxes and RY's.

Yesterday I pulled my internet computer, which I had set up for both autostart and ITTY news, and replaced it with the one running loops of newsforkids and loops of foxes and RY's

If anyone is interested, I can tell you how I set up that computer.

Tom   N3CRK