BNC Coupler that lets the user connect two BNC video cables. If you are trying to extend your existing CCTV cable by adding an extension, then this is the necessary connector to use in between the two security camera cables with Male BNC ends. It is a passive device and does not require power, nor does it amplify the signal. We do not suggest using couplers such as this for use with HD-SDI cameras.
(1) BNC Female to BNC Female Connector (aka BNC coupler)