Product Detail 360-degree, full-duplex performance for simultaneous 2-way communication 3 microphones and 1 speaker in the console; self-canceling echo Analog PBX or public switched telephone network interface Volume level adjustable up to 85 dB RCA output jack for recording or broadcasting . The "Polycom VoiceStation 100 Conference Phone System" is best product for you. We recommended Polycom VoiceStation 100 Conference Phone System