Simply cool the small part! Used by me in "Block Rocker" ION (Trolley amplifier) used and controlled via cell phone. If nothing is between them, then it works fine in a radius of about 10 meters. So you can, for example, in the living room provide a party very well on your mobile phone with music. The connection via Bluetooth works perfectly with me. Will I always buy again, if it should get away times. Is quite small and shallow - but also practical to put in your pocket. However, this part is not exactly cheap. Compare prices worthwhile. The acquisition is worth but in my opinion anyway.