Surveillance Microphones may vary slightly in their features, however most tend to have low impedance, low noise MOSFET, and an omni-directional pattern of sound recognition. They tend to differ mostly in their mounting location, the need for an interface adapter, the level of resistance to weather and corrosion, as well as the ability to adjust gain.
If you're looking to purchase a CCTV surveillance system with audio microphones already built in, here are some important considerations to keep in mind.
This product contains HFI process chip with low noise performance. Such chip can restrain noise around environment through frequency response network for several times, and provides pure tone quality and powerful movement.