The Electronic Police Siren
The first sirens were used as musical instruments, but their utility as warning devices soon became apparent and they were incorporated into police, fire, and ambulance vehicles. By combining an audible alert tone with the existing emergency light arrangements, police sirens ensured greater safety for officers and members of the public. The characteristic tritone siren, so called because it alternates between tones that are three whole notes apart on the standard musical scale, has become the standard tone pattern for police sirens throughout the country and is instantly recognizable by a majority of people. This familiarity helps to ensure that drivers and pedestrians are aware of oncoming police cars and can take steps to move to the side of the road and make way for these emergency vehicles.
While many older police sirens are mechanical devices designed to create sound by moving compressed air over small openings, electronic sirens are also available that use solid-state circuitry and speakers in order to produce the siren’s well-known sound. The older pneumatic or mechanical sirens typically used a spinning perforated disk or drum that rotates rapidly in front of a steady stream of air; the sound is produced by the flow of air through and across those small perforations.
Electronic police sirens began to gain popularity in the 1960s. Rather than using mechanical methods like disks, drums, and forced air to produce sound, these modern electronic police sirens use circuitry including modulators, oscillators, and amplifying components. The resulting synthesized sound is transmitted and broadcast through speakers that are usually attached to the front of the emergency vehicle. Depending on the speakers in use, electronic police sirens can produce extremely high-decibel sounds in a variety of tonal patterns; it’s wise to use caution when in close proximity to these piercing alarms. Extreme Tactical Dynamics offers a wide range of police sirens from basic tritone-pattern devices to advanced programmable sirens suitable for use by police departments throughout the country.
