Quoted from the Easier to read 396xt manual - You can flag a system only in the software so that it cannot be read out of the scanner, modified, or deleted. There are no settings in the scanner to do this. You can still use the system as you would normally (system/channel lockouts/unlock, volume offset, attenuate, etc), you just can't access it in the menu. Also, you can't even upload the system back to the scanner and have to delete it with the software too.