About Wireless Transmitter and Receive

Wireless transmission is considered When it is difficult for camera to use a cable to transmit video signals to the monitor. But, heavy metal walls, high voltage power lines, microwave equipment can attenuate or block the wireless signals.

FCC strictly controls the wireless transceiver system. Manufacturers initialize the commercialized models and you don't need to get a separate FCC approval. When you want to change or modify the model specification, you need to get prior approval from the FCC. Each manufacturer has unique bandwidths of frequency derived from the FCC and cannot be compatible with other manufacturer's models. 

  Most commercialized wireless systems have 4 or 10 channels, given conflicts of the overlapped channel(s), it is impossible to use more than 4 or 10 transmitters in one area. But you can increase wireless receivers as far as they are within the range.