Features: 1) PC interface supported: USB 2) Digital formats supported: MP3 / WAV / WMA 3) Signal-to-noise ratio: 87.2dB 4) Playback modes: random play 5) External hard drive function: Yes 6) Recorder additional features: variable bit-rate compatible 7) Sound output mode: stereo 8) Audio Additional features: auto-power off 9) Earphones type: binaural 10) Earphones response bandwidth: 20 - 20,000Hz 11) Voice-recording: 7 hours continually 12) Recharge time: 2 hours continually clip up lens with contours that maximize protection against sun, wind and side impact