Communications: electrical – Audible indication – Piezoelectric
Patent
1996-06-18
1997-06-10
Hofsass, Jeffery
Communications: electrical
Audible indication
Piezoelectric
3403844, 340514, G08B 310
Patent
active
056380437
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a warning apparatus which generates a warning sound for warning of a dangerous situation when this arises.
BACKGROUND ART
To warn nearby people of danger, for example when a train is approaching a railway crossing, or when an abnormal situation arises in a factory or the like, in general a warning sound is produced using a siren, a bell or the like. More recently, a speaker or a piezoelectric buzzer has been used for producing the warning sound.
With such a conventional warning apparatus wherein a dangerous situation is notified by producing a warning sound, the warning apparatus is only driven to produce the warning sound when the dangerous situation arises, while at normal safe times, it is not driven so that the warning sound is not generated.
However, in particular at factories and the like, dangerous situations wherein the warning apparatus is operated seldom arise. Hence, it cannot be known if there is a fault in the warning apparatus. It is therefore uncertain if the warning apparatus can normally produce a warning sound when a dangerous situation actually arises, so that there is extreme danger to nearby personnel in the case of a fault such that the warning sound is not sounded.
The present invention takes into consideration the above situation with the object of providing a highly reliable warning apparatus which can verify if a warning sound can be produced, even at normal safe times where it is not necessary to warn personnel.
DISCLOSURE OF THE INVENTION
Accordingly, the warning apparatus according to the present invention comprises a warning sound generating circuit which generates a warning sound within an audible frequency range when a signal indicating danger is input thereto and which generates a warning sound within an inaudible frequency range when a signal indicating safety is input thereto, and a monitoring circuit for continuously monitoring for the presence of a warning sound from the warning sound generating circuit.
With such an arrangement, when a signal indicating danger is input, a warning sound within an audible frequency range is generated, while when a signal indicating safety where a danger warning is not required is input, then a warning sound within an inaudible frequency range is generated. Hence a warning sound is heard by personnel only when warning of danger, and is not heard at the time of safety. Consequently an audible warning sound is generated at the time of danger only, with no disturbing noise at the time of safety. Moreover since when normal, the warning sound generating circuit continuously generates a warning sound which is either within an audible frequency range or within an inaudible frequency range, then by monitoring with the monitoring circuit for the presence of this warning sound, it can be verified whether or not the warning sound generating circuit is normal. It is thus possible to avoid the situation wherein at the time of danger, a warning cannot be given due to a fault.
Basically, the warning sound generating circuit comprises a voltage-frequency converter which generates an audible frequency signal when a low level voltage signal indicating danger is input thereto, and which generates an inaudible frequency signal when a high level voltage signal indicating safety is input thereto, an amplifier for amplifying an output signal from the voltage-frequency converter, and a speaker for generating a warning sound based on the output signal from the amplifier; and the monitoring circuit comprises a current sensor for detecting an input current of the speaker, an amplifier for amplifying an output from the current sensor, and a rectifying circuit for rectifying an output from the amplifier.
Moreover, a microphone which receives an output sound from the speaker may be used instead of the current sensor.
Furthermore, a piezoelectric buzzer may be used instead of the speaker, with the output sound from the piezoelectric buzzer received by a microphone.
When a piezoelectric buzzer is used instead of th
REFERENCES:
patent: 3656158 (1972-04-01), Goodwater
patent: 4554533 (1985-11-01), Bosnak
Futsuhara Koichi
Sakai Masayoshi
Hofsass Jeffery
La Anh
The Nippon Signal Co. Ltd.
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