In Sentinel it will let you add it multiple times. Both when worded exactly and with just the same frequency.Without actually trying it out, I'd say it won't duplicate it. It will probably just add it to the system in your favorites to which it belongs. You can see what it does in Sentinel if you have a system already programmed, but maybe you left out a department, which you want to add later. When you add the department, it will simply add it to the already programmed system and not create a duplicate system with only your new department.