Applies to: E1 series, Lumus, TackMix series, Duo series, B1200, D1200, RLC-523WA, RLC-511WA, RLC-830A, RLC-811A, RLC-823A, RLC-823A 16X, RLC-833A, RLC-1212A, RLC-1224A, 81MA, 81PA.

For the newer NVR (H3MB18/N2MB02/N3MB01/N6MB01/N7MB01), if you upgrade the firmware for the NVR to the latest version, it can support the 2-way audio function via Reolink Client/App when the cameras are connected.

But this function is not supported when the cameras are connected to the NVR with the hardware version H3MB02/H3MB16.

For the RLN36 NVR (N5MB01), it can not only support the 2-way audio function via Reolink Client/App when the cameras are connected but also via the NVR itself while a microphone and speaker are plugged in the AUDIO IN and AUDIO OUT ports of the RLN36 NVR.

You could use the Two-way audio function on your Reolink Client/App. 

Reolink Cameras Which Support Two-way Audio

How to Enable Two-Way Audio on Reolink Client

Enable Two-way Audio via Reolink App