Sirens

At first, a wounded man will utter a shriek. Only then he will take another action, as may be required by the circumstances. In case of the burglary and panic alarm system the simplest form of reaction to the alarm situation is activating devices to signal the alarm. There are various types of signaling devices: optical (which use light signals), acoustic (which use sound signals), or  optico-acoustical (which combine both types of signals). They can be mounted indoors or outdoors, but their function is always the same: to provide conspicuous information that an alarm situation has occurred. The "shriek" of the alarm system cannot remain unnoticed.