I don't really see a need for optos unless you've got an unusual situation, for
instance: a difference in ground potential between your rigs and the switchbox.
I did use them at one time in a homebrew SO2R controller, but only because I
had a bunch and just wanted to do something different, hi.
IMO, a simple open-collector 2N2222/2N3904 type keying circuit is perfectly
adequate for modern rigs that use a positive voltage on the keying line.
Same with the headphones, an isolation transformer is overkill if you're just
doing A/B switching between two rigs.
Others may have differing experiences, but these methods have been 100%
reliable for me. I try to keep things as simple as possible; whenever I try to
get too cute, it comes back to bite me in the butt.
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