Communications: electrical – Condition responsive indicating system – Specified indicator structure
Patent
1990-09-07
1992-04-07
Ng, Jin F.
Communications: electrical
Condition responsive indicating system
Specified indicator structure
340292, 340573, 340515, 417572, 367157, G08B 300, H04R 1700, F04B 2100
Patent
active
051032147
ABSTRACT:
The present invention comprises an audio alarm for providing a back-up acoustic output in response to a sensed parameter including a first audio alarm circuit having a first transducer for providing a first acoustic output in response to the sensed parameter, a second audio alarm circuit having a second transducer which provides the back-up acoustic output in response to a predetermined fault condition, and which is acoustically coupled to the first transducer. The second audio alarm circuit provides an electrical signal by converting the first acoustic output of the first transducer into an electrical signal. A detector circuit is connected to the first and second audio alarm circuits and responds to the sensed parameter and to the electrical signal from the second audio alarm circuit to provide the predetermined fault condition by interpreting the electrical signal from the second audio alarm circuit. After the detector circuit has determined that the predetermined fault condition exists, the detector circuit induces the second transducer to provide the back-up acoustic output as a result of the failure of the first transducer to provide the first acoustic output. The audio alarm circuit also provides several auto-diagnostic features for informing a user of internal failures in the audio alarm circuit itself.
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Curran Timothy G.
Toycen Mark A.
Griswold Gary L.
Hohenshell Jeffrey J.
Kirn Walter N.
Minnesota Mining and Manufacturing Company
Mullen Jr. Thomas J.
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