... 300HZ-400HZ6.Maximum transmission distance:3000M1.Thyssen parts,Five party talkback for interphone2.Two means of communication:Duplex and group ... control.3.The composing form is twowire system,three types voltage,24V,12V,6V;Be composed of ... be free combination to two party talkback,three party talkback,four party talkback or five party talkback.The advantage is wiring simple,free ...