Reply to post: Re: The big red button

The silence of the racks is deafening, production gear has gone dark – so which wire do we cut?

the hatter

Re: The big red button

That's what makes the APC design all the more special. It *is* a serial connection, everything looks normal with the rx/tx/rtx/cts/ground pins all where you'd expect on a DB9 with levels you'd expect. Just they chose to do.... something weird with one of the other pins (I think DTR, but could be any of the remaining ones) which means that if you're not using their own serial cable, some common line is at the wrong level, and that signals the UPS to shut down the instant you connect a a computer to it with a regular serial cable.

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