Cobra Car Alarms

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The sensor protects the inside of the vehicles cabin area by sending high frequency “sound” waves and these are measured by the receiver. Any intrusion in this space will trigger the alarm. There are two sensors situated on each side of the windscreen. These are very tiny as small as 6mm.

Ultrasonics will re-trigger a second time if a second entry takes place.

Ultrasonics also detect glass being smashed or broken. (windows must be closed when “ultrasonics are working” (not suitable for convertibles).

Car Security Sydney

A good overall sensor that covers body panels against impact, locks and glass

The “volumatic” sensor is an air pressure discriminator. It analyses the pressure in the vehicle and is equal all over the air space. Great for panel vans, SUV’s station wagons and even convertibles.

Protection Point

Cobra Protection Points



The ULTRASONIC movement sensor is designed to detect any movement in it's field path confined to the cabin area of a motor car or van. It will detect any glass being broken, forced out or smashed.

Car Security Alarm Sydney was one of the first to pioneer this type of detection in the late 1970's. Unlike some of our competitors our ultrasonic detector is "quartz" locked on it's operating frequency 40khz. This is very important as it keeps the unit perfectly stable in varying temperatures and changing conditions.

The unit is comprised of two small microphones approximately one centimeter in diameter mounted each side of the dash board. For the ultrasonic to operate the windows and sunroof must be closed. A field is set up on the "Doppler" principle using high frequency sound waves unable to be heard by human ears and the air movement in the vehicle is constantly monitored in this way. Any interference or interruption in this air space such as a window being broken of any movement in the field of the unit will cause the field to change and the analyzer circuit connected to these detectors will trigger the alarm.

For piece of mind that the interior of the vehicle is protected ultrasonic is the best alternative.

For convertible vehicles where the vehicle is left open a microwave sensors should be used.

For lock protection and to detect impact into the cabin of the area of the car a "Volumatic" sensor can be used in conjunction with the ultrasonic.


The volumatic sensor is a unique device developed to detect a forced entry into the air space of motor cars, station wagons and panel vans.

The unit can be located anywhere in the confined air space of the vehicle. It is connected to an alarm system and once activated will trigger the alarm.

The advantage of using the volumatic sensor in comparison to ultrasonic or microwave is that it gives equal cover to every corner of the vehicle where as ultrasonic is limited in the distance it will travel from it's transducer which is usually located at the front dashboard area.

The volumatic sensor is not as sensitive to wind like ultrasonic or electromagnetic field of a microwave/radar sensor.

The volumatic sensor will detect impact into the glass area such as breaking a window, impact into the door locks or sunroof.

The sensor measures inside to outside air pressure several times per second. In the case when a window is smashed the pressure in the cabin area is dramatically increased causing the sensor to trip.

With security, the more you have the safer it is!


Strike Back at Car Thieves with a Cobra

Free mobile installation in Sydney metropolitan area *
*Conditions apply

(02) 93692000