In contrast, fixed-frequency monitors respond to only one, or a few, frequencies, so they can connect to a limited number of video display boards. However, fixed-frequency monitors are less expensive than multiscanning monitors and sometimes produce sharper images.

Multiscanning monitors are also called multisync, multifrequency, and variable-frequency monitors. Increasingly, however, the term multifrequency monitor is reserved for monitors that support a fixed number of video frequencies. In contrast, multiscanning monitors scan the incoming signals and set themselves to whatever frequency range they are receiving. In practice, there is little difference between the two types of monitors because most video signals conform to one of a handful of video standards.

Also see Northern vs. Southern Hemishpere Monitors in the Did You Know . . . ? section of Webopedia.