Path: utzoo!attcan!uunet!husc6!cmcl2!rutgers!att!ttrdc!levy
From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: comp.unix.questions
Subject: Re: UPS directed system shutdown info needed
Message-ID: <3149@ttrdc.UUCP>
Date: 21 Jan 89 06:14:40 GMT
References: <210@wa3wbu.UUCP> <32@elgar.UUCP>
Organization: AT&T, Skokie, IL
Lines: 20

In article <32@elgar.UUCP>, ag@elgar.UUCP (Keith Gabryelski) writes:
< The second scenario is for any system that does not use an internal
< IPS.
< 
<     A daemon monitors a serial port for a message from the IPS tell it
<     that the system is on battery power.  Actually, the daemon blocks
<     on an open() to the serial port.  When the system goes on battery
<     power, the IPS asserts a HIGH on the DCD pin which allows the
<     open() to return.  This tells the daemon the the system is on
<     battery power.

I could see a possible problem with this if the port jams;  the UPS could
go on battery power and the system would fail to notice, nor would it notice
the fact that the port had jammed.  Mightn't it be better to have some kind
of continuous "self test" going on?
-- 
Daniel R. Levy             UNIX(R) mail:  att!ttbcad!levy
AT&T Bell Laboratories
5555 West Touhy Avenue     Any opinions expressed in the message above are
Skokie, Illinois  60077    mine, and not necessarily AT&T's.