You probably know by now but  J1 is RS232C and TB1 -1 is transmit +, TB1-2 is transmit -, TB1-3 is receive +
TB!-4 is receive-
Hope this helps
mr rtty


On Saturday, January 24, 2026 at 11:47:56 AM PST, Nick England via GreenKeys <[email protected]> wrote:


Does anyone have one of these little black boxes with a built-in loop supply?
Or a copy of Specification 50998S or the applicable Schematic Diagram (WD)?

Cheers,
Nick England K4NYW
www.navy-radio.com
Nick England K4NYW
Chapel Hill NC
www.navy-radio.com
______________________________________________________________
GreenKeys mailing list
Home: http://mailman.qth.net/mailman/listinfo/greenkeys
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]

>>> Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
>>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
>>> 1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]