Emergency communication system
An emergency, according to the Merriam-Webster dictionary, is a surprising event or group of events that needs very quick actions. Because of that, it should be very important that any communication about an emergency be well-timed and quick, so things will not be damaged or people killed. For example, during the Virginia Tech massacre, about two hours had passed before the first communication (an email) was sent to workers and students; and by that time, the person who was using the gun had already went into a building where he was going to begin his attack. In that case, it was not until about twenty minutes after the violence began, that a loudspeaker announcement was made for people to hide. In many situations, it's likely clear that just seconds and minutes are the most important for communicating during emergencies.