.lh7 .cw10 Errors Bedevil Phone Data Transmission by Matt Kramer WASHINGTON- Thå  breakuð oæ AT&Ô anä thå riså oæ alternativå  long-distancå carrieró  ió beinç blameä foò increaseä problemó witè transmittinç datá  oveò thå publiã phonå system. Thå  maladù haó severaì symptoms®  Modemó maù noô establisè  á  connectioî witè  á fello÷ computer¬  oò transmissioî qualitù maù bå poor¬  resultinç  iî garbleä  lineó  oæ  text¬  erroneouó  numberó oò lonç  stringó  oæ  "garbage¢ characters. Explanationó foò thå probleí varù widely¬  buô fe÷ telephonå systems¬ data- communicationó carrieró oò modeí companieó arå willinç tï saù whï ió tï blamå foò erroò pronå communicationó lines. More Calls Per Cable Somå  modeí manufactureró claií thå phonå serviceó arå tryinç tï pacë  morå voicå  calló intï transmissioî cables®  Telephonå spokesmeî claií thå publiã telephone network was not designed to carry data traffic. Thå  complaintó oî transmissioî qualitù echï concernó oveò thå  qualitù  oæ voicå  communications®  Theù havå meanô á growinç buisnesó foò softwarå  anä modeí  vendoró whoså productó monitoò transmissioî tï assurå itó freedoí froí errors. Still¬  transmissioî  problemó  arå noô á sourcå  oæ  constanô  irritation® "It'ó  á verù spottù problem,¢ saiä Roù Andersen¬  vicå presidenô foò producô developmenô  aô Westerî Union¬  whicè relieó oî locaì telephonå companieó foò customeò  accesó tï itó packet-switchinç datá network®  "Iî  certaiî  spots¬ tryinç  tï senä 240° bitó peò seconä ió á probleí anä iî otheò areaó 120° bpó ió  á disaster®  We'vå haä somå areaó witè sï mucè linå noiså  anä  constanô garbled characters that we had to put in a dedicated line to the customer." Manù  oæ thå complaintó havå occureä iî thå aftermatè oæ thå breakuð oæ thå AT&Ô telephonå monopoly® Althougè thå resultinç competitioî maù havå lowereä consumeò telecommunicationó prices¬ iô alsï meanô morå thaî onå companù woulä be responsible for the transmission network. "Wheî theù haä onå companù runninç thå system¬  alì lineó werå testeä everù 1°  yearó anä yoõ coulä pinpoinô wherå thå problemó were,¢ saiä Keî Krechmer¬ á  communicationó consultanô iî Mountaiî View¬  Cali®  "No÷ therå ió nï  onå company testing the lines and it's hard to track down problems." Thå  lonç  distancå  carrieró havå beeî thå focuó  oæ  severaì  complaints® "Mosô  oæ thå locaì loopó [operateä bù thå regionaì telephonå companyÝ arå nï troublå  aô  all,¢ saiä Harrù Newton¬  publisheò oæ thå  Teleconnecô  monthlù magazinå  oî telephonå systems®  "Theù havå reallù improveä thå  qualitù  oæ their service." Newtoî  sayó hå haó haä problemó usinç hió portablå computeò anä modeí witè long-distancå carriers®  "Theiò engineeró wilì telì yoõ therå ió nï problem¬ buô  wheî  I'vå traveleä arounä thå countrù witè  á  modem¬  nothinç  works,¢ Newtoî  said®  "Therå ió sï mucè noiså oî thå voicå linå thaô thå modeí doeó not pick up the connection [to the remote computer]." Otheò telephonå officialó claií somå modemó maù noô bå properlù designeä tï work with the telephone switching system. .cp3 Š "Wå havå seô uð technicaì specificationó that¬ iæ met¬ wilì allo÷ equipmenô tï  transmiô oveò thå switchinç network,¢ saiä Vaughî Williams¬  aî assistanô stafæ manageò aô Ne÷ Englanä Telephone®  "Somå manufactureró makå  equipmenô thaô  wilì meeô mosô oæ thå generaì specifications¬  buô á loô finä á waù  tï design the modem differently to cut prices." Somå phonå companieó arå usinç á ne÷ forí oæ compressioî oî thå phonå lineó calleä  adaptivå  pulse-codå modulation--á methoä oæ doublinç thå  numbeò  oæ conversations one one wire from 32 to 64. Compression Errors "Wheî theù dï that¬ theù reducå thå bandwidtè availablå tï eacè line,¢ saiä Marù Schaller¬ vicå presidenô oæ marketinç aô Telebiô Corp.¬ whicè marketó aî erroò  correctinç  modem®  "Viocå  useró  don'ô tenä  tï  notice¬  buô  thaô [compressionÝ especiallù presentó á probleí foò [modemó aó fasô aó 960°  bitó per second], which need every bit of bandwidth they can get." Schalleò  saiä high-speeä modemó incuò verù higè rateó oæ erroò wheî testeä over lines using adaptive pulse code modulation. Thå  prospecô oæ thå cominç Integrateä Serviceó Digitaì Networë (ISDN©  haó manù useró hopinç foò betteò qualitù transmissions®  ISDÎ woulä replacå  thå currenô  analoç  oò tonå baseä telephonå systeí witè aî alì  digitaì  networë morå orienteä towarä thå digital-baseä computer® Witè ISDN¬ thå digitaì linå wilì carrù multiplå voicå anä datá serviceó betweeî offices®  Iî short¬  thå phone system will become a large local area network. Buô  somå analystó arå worrieä thaô thå expansioî oæ digitaì serviceó  wilì causå  problems®  "Noiså wilì increase¬  especiallù foò thoså useró whï  arå stilì  usinç  analoç  lineó  whï won'ô switcè tï digitaì  righô  away,¢  saiä Krechmer.