... with a little amount of external components, such as audio amplifier,microphone, speakers, etc. Also adopt industrial-level design standards ... operating capacity.4) With 12-bits digital audio signal serial input, DAC audio output port,the sampling rate is 8kbps. ... : with a diameter of 2.5 audio microphone with volume control plug9) Full-duplex audio and video intercom10) Communication distance: 500m ...