RS-232 primer (WilsonMinesCo.com)

http://wilsonminesco.com/RS-232/RS-232primer.html

(formerly B&B Electronics) and Assmann:     Here are a couple of testers, first Jameco 's 26729 , then B&B Electronics' (now Advantech 's) 9PMTT :    

That's everything I could find.
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