| 000 | 00328 a2200133 4500 | ||
|---|---|---|---|
| 020 | _a0749260491 | ||
| 082 |
_a621.382 _bOPE |
||
| 090 |
_c13487 _d19850 |
||
| 245 | _aBlock 7 Digital exchanges | ||
| 260 |
_aWalton Hall _bOpen university _c1990 _g1990 |
||
| 300 |
_a108p. _c29cm |
||
| 650 | _aCommunications engineering | ||
| 942 | _cL | ||
| 999 |
_c41818 _d41818 |
||