How to protect computers from power failures.

One of the leading causes of computer data loss are electrical power problems. Brian P. Gustafson, media relations manager at Panamax, a San Rafael, California, producer of power-protection systems, describes how to safeguard data and computers against such occurrences.

In a fraction of a second an electrical power problem can immobilize a computer and destroy its data. This article describes equipment that protects computers and data from several types of electrical problems.

An interruption in power or even a slight change in the character of the electricity, however brief, cna lead to either devastating problems or an irritating assortment of intermittent computer malfuctions. There are several types of power problems:

* A blackout is a total power loss and a brownout is a voltage drop, usually evidenced by a sudden dimming of lights.

* A spike is a sudden surge of line voltage, usually caused by a malfunction at the power utility. However, a nearby lightning strike also can cause a spike--one that is so massive it can melt electrical and electronic components.

* Voltage swings are intermittent variations of the voltage level on electrical lines. They often occur in industrial parks where heavy electrical equipment is cycled on and off and in older office buildings with inadequate wiring.

COMPUTER DAMAGE

Any of these problems can cause a "head crash," a hard-disk failure that corrupts or destroys stored data. In such a failure, the hard disk's magnetized reading-writing instrument (called a "head"), which hovers a fraction of an inch above a spinning disk, crashes onto the disk's surface.

In many cases, the resulting damage is complete. The entire hard disk must be replaced; users diligent in backing up data can become operational quickly by copying their programs and files to the new disk.

Sometimes, however, the damage is so slight--corrupting only a few bytes of data--that at first it's not noticed. Partial damage can be more pesky than a total crash because the resulting problems are intermittent and unpredictable, making them hard to identify and correct.

THE SOLUTIONS

To be sure, it's impossible to guarantee the integrity of the electricity coming into an office from a power utility, but there is equipment to regulate and filter power distribution inside the building. And installing full protection is easy for both new and existing computer systems.

There are three types of power-protection devices:

* Surge protectors are situated on the electric line between the wall socket and the computer. If a spike occurs, the excess electricity is shunted to ground, sparing the computer's delicate components from the damaging surge. Quality surge protectors cost between $50 and $200.

* Voltage regulators correct small swings in the voltage level. Prices vary from $200 to as much as several thousand dollars, depending on the size of the computer system being protected. For most stand-alone computers, a regulator costing a few hundred dollars is sufficient.

* Uninterruptible power supply (UPS) units contain rechargeable batteries that store just enough electricity to allow the user enough time, in the event of a blackout or brownout, to properly save data in memory and safely turn off the machine. Many modern UPSs do triple duty: They also protect against surges and swings.

UPSs come in two varieties:

* A standby power supply (SPS) provides the computer with electricity only in an emergency. The moment the unit senses a power loss or voltage drop it can't compensate for, it discounnects the computer from the wall-socket curretn and its batteries kick in with substitute power. Prices range from $200 to $2,000.

* An on-line UPS provides the computer with full-time electricity and it's continuously being recharged from the wall socket. Thus the computer is electrically isolated from the wall socket electricity and safe from spikes and swings. During a blackout, however, it has only enough stored electricity to give the user time to close down the computer properly. Prices range from $500 to $2,000.

Which type UPS should an accountant select? Both are effective. The on-line unit has a very small safety advantage over an SPS, but because the SPS runs full-time, it tends to wear out before on-line units.

For the remainder of this article, the term "UPS" will refer to both types of units.

USER TIPS

* Not every computer needs a UPS. If the machine does not contain critical information and is not connected to a network, a surge protector will suffice. A computer linked to a network, however, requires special protection because an electrical abnormality that strikes it can spread to others on the network.

For example, a power disturbance originating at a remote terminal can travel through the data line and even harm a file server that is protected by a UPS.

* Plug a UPS into a surge protector. This doubly ensures it against damage from spikes, increasing its lifetime.

* Don't plug a printer into a UPS. Printers are not likely to be used during a power interruption. Also they draw a lot of electricity, putting a big drain on the batteries.

* Telephone lines also are susceptible to power problems. Since they connect to computers via modems, protection is needed. The best equipment is a surge protector that comes equipped with built-in telephone line protection.

ADDED INSURANCE

In addition to protecting against disaster, these components help extend computer system life by guarding against the stress of minor electronical quirks.

Accountants should consider installing power protectors on their computer systems. It's relatively inexpensive insurance.