Maximum number of simultaneous sound: 32. Input/output terminal: Stereo mini jack. Power supply: USB power adapter 5V/1 or, self-powered USB hub 5V/1A. Battery: AA batteries (alkaline/manganese/rechargeable nickel-hydrogen) x 4. Please check on the photos for detailed condition of the product.Return products must also be in its original condition: including box, packaging and all other accessories. We appreciate your business and strived to improve our customer service and our commitment to quality.