00287nam a2200109 a 450000500170000008200170001710000060003424500370004026000460007730000200012363000340014320251203091936.0  a621.3981,bD  d_  aIBM data communications Handbook  aCaliforniabNational Semiconductorsc1992  avi,c24 cm.bHB  aData Communications, handbook