On Wed, May 10, 2017 at 2:22 PM, Paul Koning via cctalk <cctalk@classiccmp.org> wrote: > I'd put it this way: For teletypes, the receiver is predominantly an > inductive load. And it wants a fairly short rise time, so you pick the time > constant you need, which gives you R, which in turn gives you the needed > drive voltage. And that works out to be a fairly high voltage in a lot of > cases, especially with the older machines with 60 mA loop current. The > needed loop R is almost entirely the series R; the receiver coil adds very > little to the total.
I'm restoring a Model 19 teletype (5-level Baudot). The current loop is 60mA, and uses 120VDC for the loop. Typical of the class. -ethan
