From my experience with ATX power supplies and IBM PCs:
There are many ways a PC can crash each needing another style of rebooting.
If it hangs but it's on, a reset will do.
If there was a power supply dropout the results are endless in manifestation
from rebooting clean (what everyone wants), rebooting but no keyboard, not
rebooting at all with or without power button functioning properly.
The last version is the worst too. In that case you have to unplug main AC
from the power supply for 5 to 10 seconds so that the +5Vst by to completely
go away then plug in main AC to the power supply and press the power button
for 3 seconds to turn the PC back on.
Since I have the BIOS option to Power on the PC after power failure I had
tested it. It does not always work. In the last scenario it does not help at
all so it's not a wise thing to rely on it.
A wise thing to do is to power the PIC from a linear source so you'll have
it work all the time and you can make the monitoring of the PC with it.
I would do like this: If the PIC does not receive a periodical signal from
the PC a certain amount of time, remove AC from the power supply with a
relay for 10 seconds, put it back, wait for 5 seconds for power good and
then hold the Green wire to GND for 5 seconds with a FET or another relay
(this is what the power button does so having two switches in parallel won't
damage nothing) to turn the PC on. Then you'll have to wait for the PC to
boot up and load the operating system. (if it has windows on it you will
have to count the time of  a scan disk at the beginning too after a crush)
and go in normal operation again.
In  my opinion an when you do something do it to work without the PC and use
the PC just for sending data and sophisticated math and display only.
This way you don'y need the telephone switch any more.

Mircea Chiriciuc
EMCO INVEST

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu