Apparatus and method of silent monitoring alarm sounders

摘要

An alarm sounder, which incorporates a piezo-electric output transducer, can be silently monitored using a variable frequency square wave. An initial frequency, close to the upper limit of human hearing, is coupled to the sounder. The transducer draws very little current at this initial frequency. The frequency of the square wave is systematically reduced, and the current draw is continually monitored. A high current indicates a low impedance type of fault. A low current throughout the frequency range indicates a potential high frequency type of fault.

主权项

1. An alarm sounder comprising:
a housing; a class-D amplifier coupled to a piezo-electric transducer, the class-D amplifier and the piezo-electric transducer are carried in the housing; and control circuits coupled to the class-D amplifier that incorporate silent testing of the alarm sounder by coupling a monitoring waveform to the class-D amplifier at an initial, selected high frequency, with a low frequency signal envelope, substantially inaudible to human hearing and a plurality of descending frequencies with the transducer current being measured at each of the frequencies.