Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: What is the voltage?
Document: There was nothing in the box but the device, no performance description not voltage limits. It would be nice to have screws for mounting, screws that mate with the holes in the bracket. Also the bracket has to be removed from the siren to allow attachment to a mounting surface. I don know why the review required &#34;20 more words&#34; to complete the review; I didn't have anything more to say about the siren.
this product is great i bought two of them they are loud as hell almost make you go deaf
this has got to be the loudest siren I've ever purchased. It's at least an order of magnitude louder than the one that came with my Astra 777 alarm. I installed it inside the car to use as a pain field type of deterrent.
something with the feq that it does something to your head. Worth the monay hands down.
it works good, can't go wrong with anything made by DEI
it is loud enough for what I purchased this unit for, troubleshooting remotely. I install this on the circuit that I need to test for power.
installed this little thing under the dash when I had my alarm  installed. its ear piercing loud and annoying!......I love it!
good and loud, expected louder as the way I understood it was suppose to inflict pain maybe if you was close by, not so but still loud enough to make someone leave that does not want to have attention paid to them.
annoying and just the way I like it.when hooked up (spliced in) with  an existing alarm systemit adds in a very annoying  sound that makes it very irritating,love itits worth it and doesn't have a cheap build quality.
after reading reviews of a small siren that was LOUD i purchased items with high hopes.after installing it  for a replacement for car alarm does not even pass across the street even barely the hoodsounds more like a child siren for a bike its not loud at all unless your 4 feetaway i would not purchase unless your going to use it indoors or in closed areasthats when siren is loud
Answer: The voltage is up to about 18 volts I recall; the higher the voltage the louder the tone.  One probably would be happy with the sound level obtained with 12 volts.  I tested it but have not installed it yet.  I either never had any instructions or have misplaced them.