I heard back from Gefen Tech Support:
My Original Question - I would like to use this product in my church. However, I want to have one video source (transmitter) and three LCD TVs (receivers) connected to it. At the moment, I plan just Full HD video (HDMI source) with no audio or control. Is this possible? If not one transmitter and three receivers, can I have 3 separate systems all operating in the same room? Distance is about 45 feet and line of sight, no walls.
Answers:
"currently you can have upto 8 senders and 1 receiver but not the other way around. Also you can have upto 4 pairs (senders & receivers) in one room as long as the sender units are 1 foot apart from each other."
"I forgot to mention the GTV-WHD-1080P-LR-BLK units can extend 100 feet with no line of sight, aslo can go through walls. The GTV-WHD-1080P-SR units can extend 80 feet but requrire line of sight."