Dwell is the time the radio monitors the control channel checking for active talkgroups before moving on to the next system. I've experimented with Viper & with it set as low as 2 (2/10s of a second), it doesn't seem to miss any active talkgroups. However I left mine set at 3. I'm sure if a system is a lot busier than Viper in our area, you will miss some active talkgroups with it set that low. On the Guilford TRS I left mine set a 0, which seems to be about 1 second. Set any lower than that it seems to miss some talkgroups.
Randy