Ideally, you should not scan a specific site more than once. You can, instead, separate the talkgroups into categories, such as PD, Fire, EMS, or any other combination. Scanning a site requires a certain amount of for the scanner to receive & decode the control data, then check for active, programmed, talkgroups. Each time it has to change systems, it adds more time, even though the same site is in use. While you can use the same site repeatedly for various combinations of departments (groups on the non-database scanners), it will slow your scanning speed, possibly causing you to miss calls as the scanner works through the sites that are used repeatedly.