How to set one of lines to be direct inward station dialing (DISD) for DSU II phone system?
Also, how to determine which outside line mapping the line port? Because we have 5 phone lines with 8 lines PBX(J0816), and it shows it detect 8 lines. Thanks very much.

Leo it is obvious that you are not an installer. Please consider hiring a certified installer to fix your issues. A one hour service call will certainly be more cost effective than posting question after question of basic installer info.

Leo AS HAS BEEN STATED HERE https://www.sundance-communications.com/forum/ultimatebb.php?/ubb/get_topic/f/2/t/001379.html If you can not follow this then call a tech you will come out way a head in the long run.