Quite frankly, I do not like how any of the original trunk trackers from either brand handle control channel dwell time. I believe it is programmable on the newer models like the PSR-500.Unidens are flawed because they scan the trunk channel for far too long (while missing conventional traffic) while GRE/Rat Shack scan it (trunk channel) like a conventional channel so you don't miss other trafffic. The 245's 5 second delay was like chinese torture not to mention the notoriously bad battery packs. Today, Uniden still scans the control channel for way too long, thus IMO, are defective radios.
Because of how trunked traffic is handled, the only workable solution for me was to use a separate scanner for trunked. Unfortunately this is a "good" thing for the manufacturers as they've just sold 2 scanners where one good one would do the job. Bean counters are only interested in their bottom line, not how good their products are.