You do not need to have the Extreme Upgrade to use ID search.
It can be selected in the Sentinel Software in the favorites list editor.
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Just to add slightly-
ID Search can be turned on (or off, if it was on) in Sentinel, then the modified Favorites list downloaded to the scanner.
With the Extreme Upgrade, you can also toggle between ID Search and ID Scan directly on the HP-2.
Similarly, you can create a new system (one not currently in the database) in Sentinel, then write the modified Favorites list to the scanner for use. With the Extreme Upgrade, you can create a new system, or edit an existing System, Department, or Channel/Talk-group ID directly on the scanner. Of course, there are other features in the Extreme Upgrade, that cannot be accomplished on the scanner, nor via Sentinel, on an HP-2 (or HP-1) that does not have the Upgrade,