00372    a2200121   4500020001500000082001500015100001800030245007600048260004800124300002200172650003500194650002100229  a0810451263  a004.6bHEL  aHeld, Gilbert  aData communication componentsbcharacteristics, operation, applications  aNew JerseybHayden book companyc1979g1979  axii, 267p.c24cm.  aINTERFACING AND COMMUNICATIONS  aCOMPUTER SCIENCE