000 00304 a2200121 4500
082 _a621.382
_bOPE
090 _c13477
_d19836
245 _aBlock 2 Communicating systems
260 _aNorthampton
_bOpen university
_c1990
_g1990
300 _a56p.
_c29cm
650 _aCOMMUNICATIONS ENGINEERING
942 _cL
999 _c41808
_d41808