Instruction: Answer the given question using the supporting document.

Input:
Question: How powerfull transformer is needed to power this alarm?  I plan to use it for my 110 v alarm system.
Document: I needed a siren to add to my alarm system, after a break in. It does the job at a reasonable price.
Excellent product, made well and wired up as an extension to our existing alarm which added two siren's to our home. It is loud and does the job that I wanted. I would recommend this product to someone to use in their alarm system.
The sound output isn't that great but keep in mind that most residential alarm system control panels allow for a combined output of about 700-1000 ma for sirens. With a typical indoor and outdoor siren, this is about the most you can expect without adding auxiliary higher power siren drivers.The warble tone is the most effective IMHO.It's cheap and works. ADT wanted around $100 for the same unit.
I purchased this siren to ad to my X-10 home security system.X-10 does not sell an exterior siren so I mated this siren along with a 12volt transformer and the X-10 light control module.The siren is loud enough to alert the neighbors and the price is very reasonable.I'm happy with results and purchase.
The siren works with my 12 alarm system and is pretty loud. I bought a spare.
I purchased this item to replace an existing siren for my home alarm system. It fit perfectly into the exterior secure box. I checked a couple of local stores and their sirens were starting at $100.00. Product works great!
It is loud,very convenient two tone choice,nice small size makes installation easy. Will operate with a12.volt battery or a suitable transformer. I recommend the product.
it was exactly what i wanted and i would recommend it to any one wanting to improve their home alarm system
actually sounds sick didn't try to return it it's mounted and needed so I'll just live with it. Maybe I'll find a good loud one later on.
Great all weather loud two mode alarm siren is just what I was looking for. I was familiar with Parts Express from a prior purchase and once again I was very pleased with the product and the service. The price could not be beat as well.
Answer: The box says 200ma at 12vdc which is 2.4va. Personally, I use a 12v battery (NP4 - 12V, 4.0ah) with a 300ma charger attached to it to power my whole alarm system, of which the alarm siren is a part. The charger is a simple 12vdc adapter that plugs into the 120 vac outlet. The purpose of the charger is to keep the battery charged, while the battery is expected to do the heavy lifting for powering the siren, buzzers, etc.If the siren is a part of an alarm system, you would want the battery to be the main power supply in case the electricity is disrupted for some reason.