my favorite commercial design "oops" was a pricey multi-port TTY
(teletype) i/o board for the then new Nova 4/X minicomputer (data
general). Worked great, as long as you only used video terminals
emulating a TTY on a current loop. Put on a _real_ teletype, and you
quickly fried the board, every time. No protection against counter-EMF.
After two board exchanges (in warranty, thankfully), we finally just
put in opto-isolators on our own TTY lines and it worked thereafter. ;-)

grins bobm
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* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
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