Calling the cell number with nothing to say is a waste of airtime. To make this useful, you would need a special voice-programmable modem where you could send AT commands that would generate voice information. But it gets really complicated (as any automated telemarketing system designer will tell you. You can't just start talking after a few seconds--the modem must understand when the cellphone is really answered, then start talking, ideally with a long message since cellphones can have highly variable reception.
This is not a good design at all. If you have inadequate or unreliable air conditioning, you are risking total loss of all computers, disks, tapedrives, and network devices in case the above system doesn't work (cellphones out of range, support people out of town, blocked roads to the data center, etc). I would never rely on the sensors in a computer to provide overtemp protection...that's not the primary purpose of a computer.
Instead, I would look at a properly sized airconditioning system with several overtemp solutions including a high temp breaker that disconnects ALL power to the data center as a last resort. There are many designs for air conditiioning systems that handle multiple failures and while this may cost some money, it's not unusual that a data center with a dozen computers to run $1 million dollars to replace and cost $10-50,000 per day in down time until the replacement systems, disks, networking, etc is replaced and reloaded. Heat damage is cumulative and while newer HP computers may shut themselves off, the external disks and tapedrives don't have that luxury and may be damaged beyond repair or worse, be very unreliable.
Bill Hassell, sysadmin
