Unlike switchers, a quad will allow you to view and record your cameras simultaneously. Similar to switchers, a quad will also allow you to pull up a single camera to full screen. And similar to switchers, some quads also include alarm inputs that basically function the same way as switchers do. By doing this, you may later be able to view a pre recorded tape and pull up a single camera to full screen view. In short, a multiplexer allows you to tape all your cameras simultaneously.
Multiplexers cost more than both switchers and quads, but are by far more flexible.
The largest concern here is cost. Bottom Line - Switchers work great and are inexpensive. All rights reserved.