The GPS RX is a tiny 12 channel GPS receiver and active antenna in one water-resistant unit. It's black with a deep blue dome, has a 1.8 metre USB cable, and measures just 50mm in diameter.

A Global Positioning System, often called a GPS or SatNav, picks up transmissions from an array of satellites, calculates its position as latitude, longitude, and height above sea level, and puts you on the map: on the road, around the town, somewhere the UK, on your boat, or anywhere in Europe. So, no chance of being lost again whilst travelling.

It plugs into your computer, takes about 45 seconds to work out its starting position, shows you exactly where you are on a map, and then re-calculates your current position every few seconds as you move.

Using the Microsoft AutoRoute 2002 European map included, it will locate specific addresses and general locations, and work out the best route. You can zoom in, add intermediate stops, change the route, and personalize the map.

If you've seen adverts for GPS units that slot into a notebook PC, remember that they may not work on a car seat as the metallic car body will screen the reception. It's not like a radio, picking up one signal: it needs to get a fix on three, at least. This receiver is on a cable so that it can be mounted on the dashboard, or on the roof using the magnets built into its base.

Although it comes with a 1.8 metre cable, if your computer is on the car's front seat and the receiver on the dash, or the roof, you may need a longer cable. Don't forget this at the shop. Also, if you travel a lot, it's good to have a spare.

Remember that, like any reveiver, the data integrity is affected by: high buildings, metal structures, tunnels, high voltage cables, and solar control glass.

The device has a hemispherical plastic body with a magnetic base. The casing contains a circuit layer, a GPS receiver, an active antenna, and a USB 1.1 interface. It can be used with an extension cable or a multi-port USB hub.

It takes power from the computer's USB socket, so doesn't need a battery or a mains adapter. It uses so little power that it doesn't even get warm when it's connected permanently.

It's CE marked, confirming that its electromagnetic radiation will not adversely effect wireless communication, and normal external electromagnetic radiation will not adversely affect its performance.

Microsoft AutoRoute 2002 European is included. The detailed map needs over 900MB of disk space, unless you choose to run it from the CD.

GPS is a billion-dollar technology. If you want to read more, there's an explanation on the technical page. But you don't need to read it to use the device.