I have a Thunderbolt 1000T on the deck behind the house... It is illegal in most places to fake an official warning signal or immitate police/fire signals. But since there isn't any "official" siren system within miles of us, I'm not immitating any official warning. I do a "test" every last Friday of the month at noon, and once in awhile I'll growl the siren for someone interested to come see it.
Most police in this area are too young to remember the Cold War siren drills, and I doubt if they would care as long as no neighbors complain about noise. I wouldn't do this at all if I lived in an area where my siren might cause a false panic.
Here's a link to the thread from when I put the siren up:
http://airraidsirens.com/forums/viewtopic.php?t=1527
Charles