Question 1

Birds can't hear ultrasonics as they have a hearing frequency lower than a human. How does this device deter birds?

Accepted Answer

I bought this a while back to stop a dog barking across the road from me. It did work against the constant barking. The owner of the dog said it was driving his dog crazy. I explained to the owner  what it was and he started taking the dog in when it got noisy. I then took the ultrasonic generator down - it had done its job!

Question 2

Is it possible to use more than 2 Piezo speakers with this? Cheers.

Accepted Answer

I use four piezoelectric speakers on mine. You could use as many as like by wiring them in a series / parallel network but probably not much point as such an arrangement simply distributes the same power output to more speakers.

Question 3

The frequency control is numbered 1 through to 10, how can you tell when its at 22Khz?

Accepted Answer

You can’t tell with any real accuracy unless you have measuring equip.  E.g. frequency counter, oscilloscope, or spectrum analyser.
 The closest you could get to a setting of 22 KHz,  and assuming the control operation is linear, which it almost certainly will be,  is to take its maximum specified frequency -  40 KHz, from memory? -  and set the control approximately 55%  clockwise from its fully anti clockwise position. 
 I’d advise you check to confirm the max frequency then apply the above method accordingly. 
I wouldn’t be too concerned about achieving great specific frequency accuracy.  I don’t think it’s all that critical in most applications.  
It’s very hard to know for sure how effective these devices  are anyway.  I bought mine to stop pigeons going into my open garage.  I believe that it has been broadly very effective.  But it hasn’t  stopped the very occasional trespasser!  I assume a small proportion of pigeons have hearing impairments. Just as humans do.
Natural selection will deal with them I guess.

Question 4

There are two wires for speakers, but it says you can connect up to 5. How? If each speaker needs a positive and negative. I don't get it.

Accepted Answer

You need to provide a parallel connection via your own circuit board or connectors. The 2 output wires would form the input to your speaker set up.

ASIN	B002SPSN7C
Best Sellers Rank	213,993 in Garden ( See Top 100 in Garden ) 2,187 in Rodent Control
Brand Name	Kemo
Customer Reviews	3.9 3.9 out of 5 stars (34)
EU Spare Part Availability Duration	1 Years
Included Components	Kemo M048 marten repellent 12 V, pack of 1.
Is Electric	Yes
Item Type Name	Kemo M048 marten repellent 12 V, pack of 1.
Item Weight	102 Grams
Manufacturer	Kemo
Manufacturer Part Number	M048N
Model Number	M048N
Number of Pieces	1
Target Species	Mosquito, Mouse, Rat
Unit Count	1.0 count

Kemo M048N Ultrasonic Generator Repels Animals, Birds and Insects. For Connecting Piezo Speakers. For Mounting in Storage Rooms, Kitchens, Warehouses, Gardens

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