The old IVS 2000 required a software disk to be loaded, plus a second one which increased the port size from 64 to 512 and added CCIS + ISDN PRI features. The IVR number, once obtained from NEC is loaded into CMD F83>0. This opened up the system to the added features and ports. Without it, you only could use one PIM (64 ports) and no CCIS or ISDN.