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I have a DTV DVR (HD pictures over coaxial cables). Recently I got an audio capable camera to add to the system. The camera has a 3.5mm audio jack. When I hook everything up and connect my cellphone to this jack, sound from the cellphone plays through the TV connected to the DVR in real time. So far, so good. But when I connect a microphone to the audio jack and talk into it, I don't hear anything. This is the microphone: https://www.jaycar.co.nz/microphone-amp-for-cctv-cameras/p/QC3434 I connect it to the camera audio jack using a cable with a 3.5mm plug at one end and 2 rca plugs at the other end as below: Any ideas why it is not working? I exchanged the microphone just in case it was faulty but that did not help.