At left is a Typical Notification device Manufactured by Wheelock you might find in a large warehouse or manufacturing facility. It is designed to get the word out when there is a problem
in a facility such as a fire or gas leak an approaching tornado and the white strobe activates and siren tones are heard followed by an announcement as to what to do. These Voice Evacuation Systems or EVAC as they have been known have been around for many years and typically where only found in big plants and auditoriums and hotels . They are not cheap to install and require all wiring to be supervised like a Fire alarm System.
But with the events of September 11th 2001 That has all changed . EVAC systems have been redesigned and bolstered to allow the general public to know there is a problem in such places as college campuses , malls etc and in Specific Military Installations.
Mass Notification Systems as there now known not only incorporate the Speakers and Strobe lights
which can be several different colors to show what is going on systems nowadays can also send out
Text and emails with warning messages and call pagers and home phone lines with messages and can automatically lock doors to prevent a threat from entering a building etc.
and provide instructions what to do during the emergency.
Reverse 911 systems can dial and send out prerecorded messages to homes in a community to warn of dangers as well. Such as gas leak , Hostage situation etc to either warn people to stay in there homes or evacuate and where the.
Dangers are as well .
To learn more about these systems check out the following link.