[Elecraft] serial cable connected to the K2 by accident

[David Woolley]

Guido Tedeschi wrote:
> <div class="moz-text-flowed" style="font-family: -moz-fixed">You can 
> also build this simple optocoupled interface:
> http://www.hamlan.org/tech/k2optocat/k2optocat.htm

That might have a use in relation to the KAP100, but it doesn't address 
the current problem, and doesn't make sense for the KIO2.

It doesn't solve the problem because it protects Auxbus by by simply not
connecting it to the cable on the outside of the KA2, leaving the signal 
vulnerable to the insertion of an incorrect cable into the connector on 
the KA2 itself.

It doesn't make sense for the KIO2, because the purpose of that is to 
generate bipolar voltages and level shift to them, the former being done 
to ensure that the full RS232 specification is met, rather than the weak 
compatibility achieved by stealing power from the fully conforming 
equipment on the other end of the cable.  This interfaces steals power 
for the actual RS232 drivers, and in a way that basically treats the 
RS232 inputs as current loop operated, rather than bipolar voltage driven.

In my view, if one wanted to opto-isolate the RS232 signals, the right 
way of doing this is to interface on the control board connector, and 
completely replace the KIO2.

-- 
David Woolley
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