Vibratone Voltage Conversion

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NJMoo3652
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Tue Nov 27, 2018 9:18 pm

Hi all,

I was looking into purchasing a lot containing quite a few items and one of them is a Federal Signal 350D vibratone horn attached below. This horn operates on 120VAC natively but I noticed a transformer on the back. What are the differences between this one and the 450D and is there a way I can convert the voltage to DC on this unit?

Thanks
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Tue Nov 27, 2018 10:13 pm

There is not a transformer on the horn. That is the coil that produces the magnetic field that causes the diaphragm to vibrate to make the sound. According to the combined datasheet I found the 350 is the AC horns and the 450 is the DC horns.
http://www.federalsignaldistribution.co ... 50_450.pdf
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NJMoo3652
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Tue Nov 27, 2018 10:42 pm

Thank you for the information. From what I can tell, there is no way to convert the AC unit to DC, correct?
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Tue Nov 27, 2018 11:06 pm

The AC version cannot be converted to DC. The AC horns use the fact that the AC reverses polarity 60 times per second to create the diaphragm vibration. The DC horns have a set of contacts to make and break the connection to the coil to mimic the effects of AC.

The more modern versions of horns use an electronic circuit to control a piezoelectric element. Piezoelectric devices are interesting in that applying an electric current to them causes vibration. That is how the electronic horns work. The reverse is true in that applying stress to a piezoelectric element causes it to produce an electric current. That is how a crystal or ceramic phono cartridge works in inexpensive record players.
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