In fact, there are many families have not just one television in their house, like living room have one, dining room have one, bedroom have one, and one cable box(set top box) can only connect one television. If need to watch three television in home, we need buy three cable box and running more long cables. That's not a good way!
But if there is a wireless device for transmitting the tv av signal from one cable box to multi room's TVs, then the problem will be resolved easily. Is there really a wireless device like this? Yes, it's av sender, also known as video sender, or wireless tv sender. There are two types of interface for it, they are RCA port and HDMI port.