[GreenKeys] Information on Electronic Systems, San Jose, CA ?

[Jones, Douglas W]

On May 26, 2014, at 1:10 PM, Ralph Irish wrote:

> ... I stumbled upon a couple of interesting, small
> circuit boards.  ...

> The other board measures 2 1/2" x 1/2" with no edge connector.
> It's decription reads:   "This board has two separate circuits.
> One converts RS-232 to a 20 mA current loop.  The other converts
> a 20 mA loop to RS-232."  (Copyright © 1978)

My device for doing this, a Dataprobe CL/232, is shown in this photo:
-- homepage.cs.uiowa.edu/~jones/pdp8/UI-8/2014/04/20-RS232converter.JPG

I got this in 1993 or so, in the original box, with manual and
schematic.  As of this spring the converter box was still in its original wrapping. This box converts from RS-232 voltage levels to either 20mA or 60mA current loop, with lots of jumpering to select among too many options, and its own power supply that can be jumpered in or out.

The CL/232 converter was made in the 1980s and never used until this year, so the first thing we did is reform the capacitors. Its power supplies are all simple linerar supplies, so the first job was to hook it to a Variac and slowly raised the line voltage over a period of a week.

		Doug Jones
		jones at cs.uiowa.edu