 However, IBM did not keep up with telecom standards on the Central Office as well as it should have; which kept IBM/ROLM from delivering an ISDN PRI solution for the 9751 until late in the game.By then, Nortel, the old AT&T (later Lucent and now Avaya) as well as others had pulled ahead and ROLM never regained ground.The Model 10 cannot use Cornet hardware (RPDN card); CORNet is a proprietary networking software (an extension of ISDN PRI protocols) for Siemens PBXs and the original 9751-9005 model.