There are two types of video balun. One is called the passive balun and the another is called the active balun. Both of it has a different function. To choose which type of video ballun to use, you should consider the distance of the video transmission.
For Passive balun, it is non-powered and can transmit video less than 1000ft, it is used on both ends.
For Active balun, it is powered and able to transmit video up to 3000ft.