NHSS

I have a situation where the person installing Pelco Spectra PTZ cameras wired both daisy chain and star configuration. Each of two controllers, pelco KBD300A with direct hookup will only work with up to 9 cameras.. They are using pelco-p 4800. My hand held tester can control them. Pelco stated I had to buy their port isolator - CM9760-CDU-T. Does a different controller have to be RS-422? Is there a better suited controller ? Since they are Pelco do I need this port isolator