Why do you need an Uninterruptible Power Supply? Here's a scenario. You've just hit record. The hard disk is spinning as it writes the track. The power suddenly goes out. The write-head on the hard disk swings uncontrollably to rest position, spitting the last bits of magnetic flux onto an intertrack spiral across the drive's platters. Your hard disk is now permanently hosed. This happened to me. I lost a 36GB Ultra160 SCSI hard drive-and all the files on it-when I had a power outage. The manufacturer of the drive sympathized but made it very clear to me that operating a hard drive without a battery- backup could result in permanent damage to the drive if the power dropped during a record cycle.
A UPS prevents you from losing your hard disk (and any unsaved work) by providing backup power if the AC line goes down. I have my MX-2424 hard-disk recorder, my DMX-R100 digital console, and two computers plugged into an APC Back-UPS ES 500 Uninterruptible Power Supply. When AC power is available, it works as a straightforward surge-protector. When the AC goes out, it kicks into battery mode and powers the devices that are connected to it.
Every summer, on wicked hot days (I'm busting out my Boston lingo here), the city of Cambridge experiences numerous brownouts due to citywide air-conditioner use. One day, during an overdub session for the new Helms record, Cambridge had three brownouts and one full-on blackout. My APC had no problem supplying me with the required 120 V through the brownouts; and during the blackout, it provided enough juice to save my projects and shut down my systems without incident.
The ES 500 has six power outlets, with two spaced for wall-warts. Three of the outlets supply battery power during outages, while all six provide surge-protected power when there's AC coming in. There's also surge protection for a DSL or phone line. USB connectivity and included software allow for automatic shutdown of computers running XP/ME/2k and Mac OS 9. OS X and Unix software is available from third parties. With a battery rated for 500 VA and 300 Watts, the ES 500 can power a typical computer setup for 18 minutes according to the manufacturer. The UPS has a piercing alarm when it goes into battery mode, and the alarm is loud enough that I can hear it over a high-volume mix during brownouts.
I used to have another brand of UPS powering my office computers. After three years, the battery died on this UPS. I couldn't find any vendors that carried replacement batteries for this brand, but APC batteries were readily available-even for discontinued models. I now have APC UPSs throughout my home, office, and studio. I even have a network-administered, rackmount APC UPS installed in my server rack. ($59 MSRP, apc.com)