EP 1174835 A2 20020123 - Audible warning devices
Title (en)
Audible warning devices
Title (de)
Akustische Warnvorrichtungen
Title (fr)
Systèmes d'avertissement audible
Publication
Application
Priority
GB 0017477 A 20000718
Abstract (en)
An audible warning device e.g. for a fire alarm system is arranged to generate an audible output signal having a first frequency 1/T1 and comprises an audible output transducer 10 and a driver circuit 12 for applying an alternating drive signal, having a second and higher frequency 1/T2, to the transducer 10 over successive distinct periods, the frequency of the periods being equal to the first frequency 1/T1. The (second) frequency at which the transducer 10 is driven is at or near the resonant frequency of the transducer 10. However, the (second) frequency signal is only applied in successive distinct periods at the (first) lower frequency and thus the transducer appears to produce an audible output signal at this lower frequency. There is also disclosed a method of tuning the a transducer to output an audible output signal at the (first) lower frequency by determining the (second) frequency at which the audible output of the transducer is high and driving the transducer 10 with a drive signal at the determined (second) frequency over successive distinct periods, the frequency of the periods being equal to the desired (first) frequency. <IMAGE>
IPC 1-7
IPC 8 full level
G08B 3/10 (2006.01)
CPC (source: EP)
G08B 3/10 (2013.01)
Designated contracting state (EPC)
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE TR
DOCDB simple family (publication)
EP 1174835 A2 20020123; EP 1174835 A3 20030305; GB 0017477 D0 20000830; GB 2368997 A 20020515; GB 2368997 B 20050511
DOCDB simple family (application)
EP 01305973 A 20010711; GB 0017477 A 20000718