I have no idea what this is called and Im not...

Question

I think this is a reciever but Im not sure. Its a black box and has the model number of RX244 on the front of it. Ojn the top of it,it has a round thing that you can turn,kinda of like an anntena. on the back left hand side ther are on/off switches 4 of them to be exact for security cameras. To the right there is a plug in that kid of looks like a s-viedo plug in but its not because above the plug it has the letters EXP. To the right of that are two RCA plugs ins, above the first one is the letter A(RCA color white) and above the second one is the letter V(RCA color yellow). On the right of the RCA plug in is the plug in for the power supply which is 12 volt power supply. Can you please tell me what this gadet is called and how I would use it with my survellance cameras please and thank you. My email is [e-mail]