Multiscan refers to a type of computer monitor that automatically matches the synchronizing signals sent from the computer's video adapter (the video circuitry). On a standard television-type monitor, the image you see is formed by a single beam of electrons scanning lickety-split across the picture tube. The beam starts at one corner, traces a narrow horizontal line, then moves down a bit and traces the next line. The speed with which the beam travels horizontally and vertically (the horizontal and vertical "scan frequencies"), must match the synchronizing signals from the computer's video circuits.
The problem is, the synch signals vary with each type of video adapter for PCs(EGAS, VGAS, Super VGA, and so on). Since the scan rate is fixed in an ordinary monitor, you can only use the monitor with one type of video adapter-a VGA monitor only works with a VGA adapter, and so on. By contrast, a multiscan monitor will work with many different types of adapters, within limits.
When you buy, be sure your monitor's range of scan frequencies matches all the adapters you may use it with. At a minimum, it should have a 50-75 Hz (hertz, times per second) vertical frequency and a 30-50 kHz (kilohertz) horizontal frequency. The vertical frequency measures how fast the entire screen is "repainted," and is also called the refresh rate. You should also insist on a variable frequency monitor, one that can match any frequency within those ranges, rather than one that simply operates at several different but fixed frequencies. And, by the way, multiscan monitors are more expensive than fixed-scan rate monitors.
There's much less inconsistency in the Macintosh world, so a multiscan monitor isn't so important. But many of them will work with a Mac