this player can work without any external speakers, so it is portable. this player has ternary jack for charging,data exchange & built-in power switch music format: MP1 / MP2 / MP3 / WMA / WAV / ASF / WMV port mode: USB 2.0 EQ mode: pop / classic / soft / jazz / dbb / rock / normal playing time: continuously playing time for 350-400 minutes after fully charged battery voltage: 3.7 V rechargeable Li battery output power : 55mw headphone output power: 5mw requency response: 20Hz-20KHz battery charge time : about 3 hours working current: 35-40 MA info/ noise ratio: 86dB Color: silver this product 's main body is headphone, and built-in mp3 and Li battery.