‘The Picturephone® System: Computer Acocss By B.S, WARWICK and C. W. PHTPPS (anus rosie Septem 1, 10) The obility to uss a Pieturepnone® sate aa to dnpley compuder ‘eneratd informetion wi be provides aban eienal futur of Pette- ‘hore aeron, ‘The baie aament cu preing campuler-acen eric tb the dinplay deta ety which acta 0s the tnkcface btaten the cmaytor tnt Bo Pisuroplone etaon, conerting Touoh-Tone® mulfrenuenay ‘guts from the Pctorephene sation ito diptal charactors forth cam. ler and converting tha computer clad ita asin vgea forthe sation, ‘The operation af the display data sted ts infonce ofthe Pokurephone ‘elon cavaseritce on te dvi are dard this ets Ti ailtion to faoe-totace eornmunicalion, lzturephona stetons ray be used to acces computers. A Pitursphone user ono eend infor- sion to the computer using bis stalion' Toweh-Tone al, and rnersape from the enupuler ean be diplayed on the Picturephone fsnreen Since the compuser-ecces capability it an alternate azo of Pietasophons savice, avd the objootive ix Via, i rot interfere with bor inezessa che coe af Tave-o-fere rertmunietion, the additional hhancwore required has heen designed so ‘hat no medificetians to he ation o7 network are ness, 1 Desription ‘Tha basie elem of ompator-neocea service ita display dats set wie aes ea ac ‘nlortue bavween the Picturephono network ind Uigte compater-onitmunieationseystom aa shown in Fig. 1. To the Pletorophone nobwork, the cispley data ott appears to be a catderd Peiwrephone siaton. ‘To the computer the display data set prevents fn interfece like those used in standard volocbond dete serves, 6 68 rn mm everpu savumen, socesat, rummcany ist “The eccentia funtion of the dn data ecb exe to oonvert Touck- ‘Tons signals zeeeived frna the salon to Agen® eharuoters wud trane- sit Ulew to the compute, fo kare ages charactor from the eom- [ter and to convert them to the video signals zeauird to reeeh the Aigplay at the station Since se display dete eat is comnestod to the Pizturephone network like a etnéard station, # mast be lowed in 8 Piceurephone service aren Tloyever, thee ave two alterstives for voaverting the display data oot to the eompuler. I tho display date set is located atthe computer ste, a dirt eile eonnetion is maze to the computer. Tf ‘the deplay data sie Jaen! remate from th computer, m dsc foarwinovoieeband data link is used to connect the display data eet tnd computer; this the womputer ean be Inealnd ouside of the Pic- turephone eervioe area, The econone decision aeoting display dat Sev latin is governed by Ue cost trade-off betscon ewitebed video facili and dediatad voieoband fadites. The eoxputer communi fates with a dlstare eiaplay dice eek in ase asynchronously at a 1a00-baud rte, The comptter and cisplay data el are dizetly eon rogéed,eotmunication is possible at either 1200 or 2400 baud "The dizpny dla sti conbectad over a standard Picturephone lop to # cratze elie, rive branch exchange, or key lelephone eyetem. On etched zetworc, ican be teeed remotely from a te desk in the sema maner ce « Pstwrephone station’ A lopheck festure in the display data set allows lst dekman to send Peuch-Tone signals forthe ect andl see that on the goreen of Bs Pctarephone sot; this peacinn Netioel Sind Cr fr Tafomaticn Interchange (ANS 24 wi ‘conrren scenes 85 provides a rimple, lu thorough, else of dhe display dats ect opera thon. For eaaes whore a voieeband deta Tink tweed beteaen the dzplay ‘late set id eomputr,rwuble ication procedures allow theca: deck ‘mea to determine whetaer a trouble iv in the Piturephona netwoo the displey date est, or inthe voiodsand det link. 422 Operation ‘A user ean place a cll to the display data set and computer just ss be would to another ration, Referring to Tig 2 ell to Uh eo pulor is anewored Uy the Boll Syeium 40812 Data Sol# The user ean ‘hen tend messages to the computer wing his Touch-Pove dnl, The 4032 Daca Be. ronvera the Tovet-ona signal to canta’ conures, which che dlpiny dasa se: eoxverss to serial ascar and transmis to {he eompuser av 1200 oF 2400 bun "The eormouter responds to mvsevacs froma the weer with looks of up to 440 alphamomaric charactors, Those blovks are revived neyn~ thronously st 1200 or 2400 buds nd sired in @ refresher memory. From these blocks, the display dato sot forms displays of 20 ines of tp ta 99 characters each. The content of the memory ie convartad to ‘interlaced video eignal, mixed wich eynebronning informatica, a Innit to he station aa required to retzech the display 20 times pe aecond ig. 2 utrepons empties Mek gr 688m um oraruae racuincen JouMeAL, FeaRUARY 167 iguee 3 and 4 show sample deplays on w Piaturephone set. The fiplay dats. eet can gencexte A alphanumeric characers and 16 traph characters; these cee shown in Fig. 6. ‘Tha graticue is cle played wherever eny graph charuetere are shown, Wor offing displeys fae user haa the option of using an alpha fe hepburn frequency sbi" eying data rob (euch asthe Bell System 118A Date Set) in conjuneion with bie Pizturegtons station, When this it done, 110-bouderial aso signals from the wa~ ton are recived by the ell Systam 108A Dla Bet? (See Fis. 2] ‘and epeed-oonverted fo 1200 or 2400 bauds before being sent to the Computer, With fe dipiay dete ae in th ed mode, gm alphanumeric Ieeyboend cua by wel lo realty ths contents of Lie tefresher memory. ‘A tnovable biking eanor, whieh marks the leswion of the nett har fuer vo be written in the enony, ia disyed in tho edit mode vo thd the urer ia auering displays. While in the eit mode, character: recvived ‘rom the keynant ane used only to update the ceplay date concen. scorer esr Mig. typi phe see set meocy; hey ave not sent to the computer, When the user zalised with ihe dieply, fe can requent the daplay data oe to trans rat the eononts of the referer mamary tothe computer for storege or provemsing. This festure allows user Uo retrewe fle feors the fommpster, to modify or ulate shese Gls, and up weal updated Bes ‘aes to she eompator Trg the all, the display sna sel gtinaes to peroen te conversion foneions, Handling ini ead omer responses aa required 'The information metrievs! and input ospabilties evaiiable to user of Pitwreghone eompter-arooss service are luge «lune tion of the eustomer-povided programs. The display date ect bus boon designed not to interfere with o> zeagt to mane egnals rent from the user fo the compiler, Ieing most decisions acting message formate end intemetive procedures la Ue customer sn prograr designer, Further, the display data sot operation iv amerally under fompatas control; hat i, exept when She eiing Fealure in enabled, 688 nuLy wus, sve MAMIE JOUNAy sR LOT the user sends a request te che computer ard the sompuler signals the dioiay data set respond to che royce! 'A calls loinaled 2 any time af eithor the aoe hangs wp oF th comptes tits eneef-eall gc 2. Sambal Formalin aad Screen Copocity ‘Whe maxizum number of eharscten in a single display iv doter- sined by vonsidersions of verve sive and shape, Picturephonerastor parameters, bandwidth und aonlizeriirs of Me vetworke snd station sel, roel Tegbiliny of tho routing fout.« The maxinum number of harnetore per line was choaen Ey an etpiiea evaluation of several Glifercs curucle shapes td snes, A judgment waa thea made Uh ‘minimum leneth wiile-wznen ehould be aboat 06 us and te mini sum black sogent aout 0.78 ys, making a bluek-ite pair wt lous 1125 yt Jong, By choosing special designs for come chamctrsfece Fig. covrenen access 9 6) ae maximum mursber of black-white pair, including the spice between characlre, wae limited to three par character, Thos the ‘minis length ofa character space s 3.76. This eclte in w oex- ‘mum of 22 eharecens being daplayable, sa the visible portion of & lociaaatal sean ine i wpprenimatoly #5 po aking into account worst- ‘ace Pictwtophone parameters and allowing apace for margin on the Side of the dip, "The elphenwmerie apmbole ia the dep xb ane contract on the baci of 0.95 v3 subsegmenc oF a sesm “ne, witt each white seamaont Tbaving at Kos bo stbsogmente and end ilae segment having ut Toast thre aubseemenes, This ellowe mone Aexblity ia chaneice de- sig thea if Jsgcr aubeogment length hed boon chactn, A chenectar lise w 2subvepment horvontal diners and an doterclemeter spacing of three subscgments is provided for totul of 15 subsrements ina character mace, The reslting cheraeter widths sre a maximum 0.165 Snahes (0-42 em. Tntesohavasterenasing ia 1042 snches (0.11 ‘on ta OUT ihe (0.17 em) depending, an the patientar characters, "Tae maximum number of lines of skuntelers be dedermized by the snuuber of sean Hines avalsble, Hecasee the Pisturaphone sxeea fot exactly nestengiler, and ceeourting for worst-caee parameters ‘nd muagion on the tep and bottom af the display, only bon 207 team Fines mill aya have she fll fey eworp veble, Basod en ex pital studies, even teun ‘inex wore elowon ws the were! cimension for the character sot. Allowing em intrline spacing of thre sean lines lrought the tote to tan seen lines per lin of ehnreetere. Therefore, 20 Wve of tax: oan be dieplayed. Charactor heights are thus 0.4 inches (088 rea) with an interline spacing of O16 incber (0.15 ex). "The sinleen graph ehaneeters bom in Hig. 6 may be used to die play simple carves and bur charts, Ia xfer to provide goed peint mci Tor graphs and continaty when ereating bes chart, Chow Characters wero chosen to be fe seab Tnes high aad 14 eubvegmente ‘wide on tho Triana] dirtension. (The grtieule ooeapies te 15th imbsegment to provide Horiaen:] corteal yt ‘Ar mentioned above the churislerchapos chown in Fig. 6 were de- vermined expiiclly, although senre chamigos havo been Teade in thet sign basod on experimental uso. Sublostve experimente are being run lo compare the lopbihty ofthe present font with eltematives, for ‘example, a font with lager ehariclere gm inerosed interline spacing, Took wich fewer pocsible character per display. The eects of trans rion impairments and dist] enceding end dosoding ox the dif tnt fonts ate alzo being evaloater, 90 rm ms rmrme necHENACAL JOR, rOmADAMY ter 14 Signal Shaping and Spectrum ‘The minimum whiva sew ive segment of 5 ps ned to form char scters has a fandarentel eowronent at 1 MH. Thie isa: the upper fd of the Pichwephone system handiath (atalion-o-station) whieh is dow 20 dB a2 1 AGLls, ‘The Jong, harzostal parts of levers, ach a3 tho top ofthe letter K, are 26 ge i wilh with @ fundomental com- ponents 00 KH, Thi sults i the horioatal paris of letery being Touch brighter than (he saerow vertical paris wd greatly increases the apparent Seker of displays. Th meke letzer evenly bvighk, the en Ietaubseganera of hie interval on can line ere main tained at fll ainplitide rele se ride white sobsegments are 7 duced some 20 percent in amplitude, Fizure 8 shu ihe eect of thie shping on egos "The wharp Bisck-to-wbite aed whiteto-black transitions interent in compulersqenerated digplays und (he regulasity of theo tenstions five churucer epasing can vera in an on-line signal with fre- quency epecun iva unlike & typical (acstonane signal Figure Te hws the power spectrum for a dislny of text, (The antance "Now the tine for ull gvod wen to come to the sid of the party” wee ‘repeated to fill 20 lines of 22 ehuruclors) The spectrum of a fac-tor Tee igual is hows in ig. 7b for comparivon, Aa shown, oarain Twente of the borkontal spre rato are emptasied by the 2yn- hronous asture of the aiphagmenie dislay, These harmor‘es are Tocuiod at 1/276 pa 2/875 us, cte, where 8.75 yo ie the horzonia] ccharuler spacing, The snplilude weighting of ho n/2.76 ps spoon] Tinee is diferent for diferen- diplaye. Wer example, if @ page full of <q + nt al — ig Vien se! fore and ter shaping. ‘courcri soca oo ef et ot ite dn i. (Pee 002 nu en exsiuse mmmnsi0Ms soDRNAE, rmoMUARE Tmt “Te were transmited, the greulml poster donsty would oscar 18.75 gs, whorear if page fll of "73" were tranamiti, with two vertieel etree per character, the greatest. density would oomr at 2/8. as. Siilar considerations resul: in sideband at multiples of 1625 He on thet harmonise, The eeltivaly high power density pale in the display data set signal and possible siilar signals generated bey Pieturephone stations in the graphies made are a factor in the ‘anamiesion exzinaring of the nelwork to inguro that uch signals ‘ll not eauseexcesiveintorforenan into other Pcturepkone cinaita™* 441 Loic Create and Storer ‘The bale of the logo in the display dete set is consructed wath ‘Western Elootsie RTT. log ship, coded 1, 11 ant TT, These are respectively » quid 2iaput yale, a dual bufler and a dual type-D Aipeop, The contact elware/seca esnslator and svial eutputeeguit tee commercial TJ. ivuit, The tefrnber memory i composed of tommerial MOS stati wily registers. The aseu/rideo paern irae later employe o eemrcial Waided transicrmor eaonly memory. 4.2 Caneel Sytem Organisation ‘A block dicgrem of sbe digplay ésie ect is sham in Fig. 8 Serial sou charactors from the aomputar {or the eustomner keyboerd when in the eit mode) are stmpled an convered to parallel informetion fr the roirnher memory, Contol characore are als detected. igure 9 howe pwc of typical line of characters us displayed on 1s Pleturephone eeren, The Piturephone statin is refreded with Lwn fiad-intrlacod. elds, one every 1/60th of a socond.* Therefaro, the ‘odd sean lines in ear Tine uf shavacters on the screen nro displayed fn one field and the even ean lines on the next field, Besguse the ‘character ps intesine spacing is tem sean Tine ig with five linet in cach fle, the ssor information eoorsponcing o one Tine of chet- ancefe on the Piotrephone caren must bo preonied for tracsieion ta ideo signals by the sem/viceo pastam translater (Fig. 8} Sve times before moving on tothe next Lina of ebaractara. A cam be seo 31 Hig. 8 tho rlvesber stove is cvided into two pars, one conection of ‘the entixe display, ene Ube reeaher store, ad the other of cho line of sharaetars being scanned onto the eereen a the moment, esled the Tine stare. Thase ta pars of the refresher memory are wynohre- nized und operated in & strt-stop mode, so tt the required spect