Hmmmm.... good question. When I bought my second camera, I bought the same brand, just to be sure. Hope someone can give you a better answer. I bought a wireless B/W system from Radio Shack. It works great! It even goes through the ground , through a stone wall , and wood wall ! $ 99. Can't beat that!
I too have a wireless camera from Radio Shack. One color camera and the reciever is 320 feet away from the barn in my house. But was told I could only add the same camera brand. Which at the current time is not ava. to buy only the camera....$129.00 with a 3 yr warrenty...The pic is perfect!!!