The principle of operation of the alarm siren is to alert with a light or sound of an alarm. The alarm control unit sends a notification, after which the siren is activated. Sirens, the signal of which is triggered in the form of a sound, are called sound sirens. Alarm devices including both sound and light — light and sound sirens. Sound alerts come in different tones, with power of up to 110 dB (pulsating or continuous). The light alert may look like a flashing light. The purpose of the siren is internal and external. The external siren works in a wide temperature range and its body is protected from moisture and is more robust than internal.  The place of attachment depends on the type of installation of the siren — external detectors must be mounted in places that are protected from any weather conditions (snow, rain, icing). The optimal power of the device depends on the place of installation of the siren for the security alarm system (indoors or outdoors) — the siren with a power up to 100 dB is used indoors. On the street, an important role is played by the distance at which the sound of the detector and the presence of extraneous noise (for example, cars) should be heard, so the external security siren should emit a sound of 100-120 dB. Sirens for burglar alarms are equipped with a tamper — a device that is activated when the case is opened or the siren is removed from the wall and thus protects the detector from intruders.