Audible Signalling - AUER - #1

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TYPES OF AUDIBLE SIGNALLING DEVICES Electromechanical horns and bells Function: by magnetic force (coil) a tappet is moved and hits with a frequency of 100 — 150 Hz on a métal membrane. This results in the typical low frequency and well audible horn tone. In a bell the tappet hits a bell dome which produces the typical bell tone. Motor sirens The motor siren produces a classic unmistakable siren tone. Due to the high current consumption it can how-ever not be used for continuous opération. The sound is constantly emitted (symmetrically) which is in comparison with loudspeaker products an advantage for certain applications. Piezo buzzer Piezo crystals have the property to change their form when switching voltage. Mounted ob a brass plate this is used to producevibrations on the plate and by doing so produce sound. With respective constructive measures (résonance principle) one can auditory threshold (H) achieve very high sound pres­sure levels (approx. 107 dB buzzer module modulSIGNAL.70 signal tower). The nominal current remains low. Fréquences from 2000 -4000 Hz are achievable. Electronic sounders The acustic signal is produced by a microprocessor, electronically amplified and emitted via a loud­speaker. Electronic sounders can produce différent type of tones and frequencies. The sound pattern is (depending on the quality of the loudspeaker) very good, as différent tone types are avail­able several well distinguishable signalling tones or also customized spécial solutions can be made available. As loudspeaker sound capsules and/or classic loudspeakers are used in smaller devices, for more powerful devices pressure chamber loudspeakers are used.