Our DVR has four audio input ports and one audio output port, you need to purchase a security microphone, and use audio cable to connect it in a location where you want to capture audio, then connect a loudspeaker to the audio output port.
If you need to capture audio at various locations, your best bet is to purchase mic’s for each location and run them through an audio-mixer, with the output from the mixer going into the single audio recording input on the DVR.
The below is the diagram for your reference.
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