Strobe Lights

For most alarm systems a flashing strobe light is required as well as the internal and external sounders and is mounted on the external bell box. There are two reasons for using a visual indication such as a strobe light:

1. When a system activates in a built up area it is not always easy to pinpoint which alarm it is. This is especially true when inside a car. However, by using a flashing light the task will be made simpler.
2. With some alarm standards the external sounder is required to stop after 30 minutes. With control panels which do not have an auto-reset, the strobe light is connected to the internal bell output and will continue to flash after the external bell has stopped.

Operation

A strobe light consists of a sealed u-shaped glass tube filled with xenon gas {similar to neon gas in neon lights}. Two electrodes are placed at each end of the tube and a high potential voltage is developed across it. This causes the gas to become incandescent (light up). A charging circuit is used to bring the 12VDC from the control panel up to the required voltage. Once this voltage has been reached the tube will flash for a split second. It will then take a short time for the circuit to reach the required voltage again. Typically a strobe light will flash at a rate of about 50 – 70 times a minute. The operation is similar to that of a flash on a camera.