Putting analog CCTV signals onto UTP cable requires the conversion of the unbalanced BNC output of the camera into a balanced signal that can be carried on one pair of the UTP. When the signal reaches the head end/recorder, the signal must be reconverted so that it can be connected properly with a standard BNC-type connector.
The baluns, which perform the conversion of the coax output of the typical camera to a UTP-friendly signal, are available in passive and active versions. While passive baluns just convert the signal, active baluns provide an amplification method, which increases the potential distance of transmission.