UPS directed system shutdown info needed

[clewis at ecicrl.UUCP]

In article <210 at wa3wbu.UUCP> john at wa3wbu.UUCP (John Gayman) writes:
>
>    My question is, how are these interfaces being handled by small Unix
>boxes ?  I'm using a 386 machine running Microport V/386. What would
>it take to have the system shutdown (logically) from a signal on an UPS ?
>I assume most UPS's interfaces simply bring a signal low (or high) and
>its up to the system to act upon it ?  Or does the UPS carry on a 
>dialog with the CPU ? (ie: Pssst, I have 3 minutes left, watta ya wanna
>do, shutdown or go for broke ? Well punk, do ya feel lucky ?)

The ones I've seen have only two lines:
	- one to the computer saying "AC Gone!"
	- one to the UPS saying "shutdown completely".

Twould be also nice to have a "n minute warning"...


Altos machines have some sort of hardware/software package to use some
UPS's.  So does Novell for messydos.

What you can do if you have a serial port to burn, is to connect the
"AC Gone!" wire to receive data or CD or something, and have a bit of
software waiting for a transition on that line.  When it sees it,
it does:
	echo bye bye | /etc/wall
	sleep 20
	/etc/telinit 0
(or some such).

You'll have to ensure that the voltages are okay (< +-12) and
that the transition can be reliably detected.  Might even be able
to do it without losing the port...
-- 
Chris Lewis, Markham, Ontario, Canada
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