Wide-band acoustic echo cancellation with HD-voice dynamic noise suppression, automatic gain control, voice band equalization and intelligent microphone mixing. Best for conference room within 30 Square meters and supports audio teleconferencing within 10 attendees. 4 inner uni-directional microphones gather over 3m, 360 degree range.Support analog PBX, PSTN and analog telephone network. Smart recording feature: Recording your meetings smartly, recording length up to 550 hours, recording distance up to 5m with HD-voice. Playback feature: recordings can be played back on your device so that you can listen to the meeting contents or you can play back on a media player.