This will either alleviate or generate confusion. . .
Scanner models that are NOT HP (HP1, 436 or 536) have pre-programmed frequencies in their internal memory. These are frequencies that were valid at the time of the scanner's development. That goes back a few years. Since then, two things have happened in radio communications. Re-banding and narrow-banding. Re-banding caused a shift in frequencies for many trunked systems. Narrow-banding "tightened-up" radio frequencies and in some cases, resulted in new frequencies being used.
Thus these "Non-HP" scanners have outdated data in their internal memory. The fix is to re-program the appropriate systems using a computer program and downloading the most recent data from the RR database (premium subscription needed).
The newer "HP" model scanners, as part of their initial set-up process, go in and grab the most recent RR database information.