DURAGADGET Portable USB Powered Speakers For Tesco 7" Portable DVD Player TC7PDVD / T7PDVD113 & Bush 12 Inch Portable DVD Player Active portable speakers, ideal for laptops Power supply via USB port (bus-powered) with a 3.5mm Jack Plug Volume control dial Frequency range: 320 Hz - 20 kHz Sine-wave power output: 2x 180 mW (total harmonic distortion &lt;3%)