Tools Of The Trade: The RS 500 VA uninterruptible power supply

Large businesses might invest heavily in protecting their critical computer systems, often housing them in a purpose-built facility in a secure building, with advanced ventilation and power-supply systems.

For smaller businesses, and home computer users, such measures aren't practical. But it is relatively cheap and easy to guard against one of the most common problems affecting computers: the spikes, surges and temporary power failures that can wipe out a user's work.

The RS 500 VA from American Power Conversion aims to provide stable flows of power to a desktop machine or small server. The compact box, designed to sit between the mains outlet and the computer's power input, regulates the supply, preventing problems with spikes and surges. A built-in battery gives standby power.

A typical "tower" server can run for around 20 minutes off the RS 500 VA's battery. In the event of a temporary power problem, this should allow the system to continue working without interruption.

No RS 500 VA can keep going indefinitely if the power fails for longer periods. At some point, the internal battery will drain down. But in a small business environment, it should give enough time to shut down equipment without work being lost.

The APC range of power supplies provides PowerChute software to do this, which is extremely useful for computers that stay on out of hours, when there might be no one available to shut the systems down.

You can, for example, set the RS 500 VA so it powers down the server when there is five minutes' capacity left in the battery, or after a given period of running on backup power.

Once the RS 500 VA is set up, it is designed to stay running and needs almost no maintenance. Installing the unit is easy and it brings enormous peace of mind.

The hardest task is probably deciding which RS 500 VA to opt for, as APC has dozens of models with a range of capacities. But given the benefits and the relatively low cost - the model reviewed here gives change from £100 - installing one should be an easy decision.

RATING: 5 out of 5.

PROS: easy to set up, peace of mind, good value.

CONS: none to speak of.

COST: £79.

CONTACT: www.apc.com