New York City Homeowner's Guide -
Alarm systems (part 2)
Audible alarms are recommended over silent alarms for residential use
and reliable alarms should include:
1. A battery-powered fail-safe back-up.
2. A rearming capability and siren timer shut-off.
3. Read-out ability to check that the system works.
4. A siren sounding device that can be installed on the exterior of
the home to alert neighbours of possible intrusion.