[App_rpt] Cannot understand Radio requirements

Dear All, I am very interested in using the radio option in conjunction with my already created asterisk network, but I have no experience in the radio part nor have I any close idea about. I studied this application requirements and saw the hardware needed they describe a radio quad which uses RJ 45 but I can't see where the RJ goes in order to be able to communicate with the radio devices, I have absolutely no knowledge in two way radio devices so I hope some one could complete the full picture for me behind the radio quad. And what I plan to use this feature is to expand my * PBX network to remote sites and use it to talk to onsite engineers through the two way radio devices using iaxrpt. -- Thx MAG