File Number TP-09 Form GA24-3415-2
Systems Reference Library
IBM 2741 Communication Terminal
This publication describes the application areas, principles of operation, line-control signals, and special features of the IBM 2741 Communication Terminal. The communications facilities and data sets that can be used with this teleprocessing terminal are discussed. Also included are a glossary of communications terms used in this publication, timing considerations, code charts, and keyboard arrangements. Third Edition
Tbis is a n1ajor revision of, and obsoletes, _l\24-3415-1 ~ The tf'rrni.nal tr:m.;,n1ission controls and the Selectric typewriter controls arc no longer described Jn this publica tion, and arc now included in the SRL publication, JBM 2740/2741 Comnnmications Tcrminal--Operator's Guide, Form CA27-300L For information on other IBM Tele proce$sing products, see lllM SRL Bibliography Supplement~- Teleprocessing, Form GA24-3089.
Th1:~ users of this rnanual are cautjoned that specifications are subject to cbange at any time and without prior notice by JB1vl. Significant changes or additions to the specifications contained in this publicatjon will be reported in subsequent revisions or Technical l'-...e,vs.lc:tters~
Copies of t11fr and other IBM publications can be obtained through local JBM Branch Offices.
This manual was prepared by the Systems Development Division, Address comments about this manual to Publications Center, Department E01, Systems Development Division, P.O. Box 12275, Research Triangle Park, Nmth Carolina 27709, Page of GA24-3415-2 Revised Feb. 3, 1970 By TNL: GN27-3053
CONTENTS
IBM 27 41 COMMUNICATIONS TERMINAL 5 SPECIAL FEATURES 13 Communications Terminal Concepts 5 Typamatic Keys 13 A PP LI CA TIO NS 7 Receive Interrupt 13 On-Line Scientific Computation 7 Transmit Interrupt 13 On-Line Computer Programming 7 Print Inhibit 13 Text Handling 7 Dial Up 13 IBM 2741 COMMUNICATIONS TERMINAL DESCRIPTION 9 Pin-Feed Platens 13 IBM 2741 Keyboard 9 COMMUNICATIONS CONS IDE RA TIO NS 14 IBM 2741 PRINCIPIES OF OPERATION 11 IBM Line Adapter (Limited Distance Type 1) 14 General Operation 11 IBM Line Adapter (Limited Distance Type 2) 14 Modes of Operation 11 IBM Line Adapter (Leased Line) 14 IBM 2741 Line Control 11 IBM Line Adapter (Shared Line) 14 Prograrnn1ing Considerations 11 Keyboard Considerations 12 CODE CIIARTS AND KEYBOARD ARRANGEMENTS 15 Timing Considerations 12 GLOSSARY OF TERMS 21
iii
IBM 2741 COMMUNICATIONS TERMINAL
The IBM 2741 Communications Terminal is a re techniques, the concept of one-operation-at-a-time mote input/output terminal providing direct access remains basic to most applications. to a computer such as an IBM System/360 through At present, the central processing unit (CPU) a multiplexor such as an IBM 2701 Data Adapter does, in fact, do one operation at a time. (This is Unit, 2702 or 2703 Transmission Control Unit, or an oversimplification, since separate operations an IBM 2712 Remote Multiplexor connected to a 2702 may be carried on by an input or output unit, a chm1- or 2703. Hereafter these units will be referred to nel, or a directly connected CPU; or these operations as multiplexors for ease of reading. The terminal may be overlapped. ) However, these one-at-a-time (Figure 1) is an IBM Selectric@typewriter with the operations take place at a very high speed measured electronic controls necessary to enable it to com in microseconds and nanoseconds. The rapidly de municate with the System/360. It is designed to veloping field of multiple programming is one aspect operate as a remote conversational terminal, en of this advance. Why wait for a card to be read? tirely dependent on specific computer programs. It takes about a tenth of a second. Switch to another This dependency makes computer control of all job and work on it until the information from the program procedures possible, thereby relieving the card has been delivered. terminal operator of these details. Each 27 41 is Another concept applicable to usual uses of the connected to the System/3GO through a multiplexor computer is that of minimizing the requirement for by either a privately owned or a common-carrier human intervention. Since the machines are very provided communications•line. Only one 2741 is fats, they need not wait for people to sense a signal, comiected to a line, thus providing direct and im think, and react, since this will result in a time mediate access to the computer. The 27 41 is delay. ideally suited for text handling, on-line computation, The IBM 2741 Communications Terminal is a and programming applications. Its use can be ex step into a new application a.rea where these concepts panded, however, to include any application area no longer apply. The computer handles many dif requiring a conversational mode of operation, lim ferent jobs concurrently and each step of each job is ited only by the bounds of the programmer's cre under the control of an operator. ativity and ingenuity. With the IBM 2741, the power When handling text, the computer does not calcu and versatility of the modern data processing system late or analyze the "data" or text entered into it. is available to the user of a simple, low-cost type The information coming in from many terminals is writer terminal. simply stored in order, with the codes defining sen One IBM System/360 and multiplexor can service tences, paragraphs, charts, and space for figures. many IBM 27
The potential of the electronic data processing ma chine is constantly being explored. The early use 2741 l=====l System/360 of the computer in accounting applications involved one given set of information (punched in cards). A 2741 fixed series of operations was performed upon each set of data (record). If a file of cards was to be up dated, the changes were also punched into cards a.-id ----1..ommunication Line collated into the master file before the processing 2741 =Multiwire Cable began. Then, a new file was punched by the com puter. With the use of magnetic tape, three tapes *If a 2712 Remote Multiplexor is used, it must were used to streamline this typical operation. The connect to a 2702 or 2703 Tronsm ission Control old file, the changes, and the new file were separate. Unit which in turn connects to the System/360. Even with numerous improvements in machines and Figure 2, System Configuration
5 relatively long time to perform operations, the com time-sharing, a number of terminals are connected puter is able to switch electronically from terminal to the computer, each holding control of the com to terminal and keep incoming and outgoing data in puter intermittently; specialized jobs are efficiently order. handled. The program used to accomplish this A request to retrieve the stored text includes for would include a phase (routines) to keep track of the mat instructions. Then the computer operates upon communications and whatever working phases are the data. It divides the text up into lines of specified desired, These working phases might include a length. If right margins are to be justified, spaces modified Fortran compiler for computation, an as are inserted between words in a specific pattern to sembler for programming, or a library and modified accomplish this. Between servicing the other term input/ output control phase for information retrieval. inals and executing similar operations, the computer Basic to time-sharing and text handling is the sends the text to the proper terminal at the maximum idea of "mm1-machine conversation." An individual rate of the terminal. enters some information into the computer. The The text-handling capability of a multiterminal computer processes the information. This action computer is only one aspect of this relatively new may be formatting, computation, a search for and concept: time-sharing. Many people, each at his retrieval of additional data, or a combination of own terminal, can be using the computer concur these. The result is returned to the person. In the rently. This utilizes efficiently the capabilities of case of text handling, the result is accumulated in the computer. Time-sharing is applicable to such the computer and may be modified. With time areas as engineering, programming, education, and sharing, the computation might, for example, in design, as well as text handling. clude the loading of a routine to solve a differential Without time-sharing, data is processed by per equation and the solution of that equation with a given forming one (or a few) identical operations repeat set of parameters. Typically, the computer relieves edly on similar records of data. However, the speed the operator of most of the time-consuming, repeti and versatility of the computer are advantageous in tious details associated with creative work. The many other fields. When the processing of smaller, output of the operator can be expected to rise in more specialized jobs is limited to purely scientific quality as well as quantity. installations, utilization is not high. Now, with
6 APPLICATIONS
The IBM 2741 is designed to require minimum oper The computer can replace the libraries of catalogs ator training. The terminal, considered by itself, and, more importantly, the indexes of catalogs used is a typewriter capable of maintaining line control, to maintain reference material. A simple example encoding the characters typed, and presenting the is the card catalog of a library. Entries arc coded signal to a communication channel. (See Communi by subject, author, and title. Such a method is cations Considerations and IBM 27 41 Line Control readily adaptable to a time-sharing system. This sections). Therefore, the applications of this type of cataloging is common throughout the business, terminal are determined by the program used by the scientific, engineering, academic, and governmental computer. Scientific computation, computer pro worlds. A computer time-sharing system can pro gramming, document preparation, and information vide fast response, easy updating, and convenient retrieval are some areas of time--sharing appli remote inquiry. cation. Text Handling On-Line Scientific Computation These terminals arc used in a new approach to the Many approaches are possible in the area of com production of large-volume transcriptions. Text putation. The entire problem may be defined by the hm1cUing is a specialized application of the time operator in a symbolic language such as Fortran. sharing concept. Text that has been typed and en This method i.s useful when a complex equation is tered into accessible storage is proofread ru1d edited. not encountered frequently. Variables maybe changed The typist then revises the stored text a8 required and a new answer obtained without re-entering with deletion and insertion facilitated by the com the equation or unchanged data. An alternate 1 puter. A copy of the updated draft or parts .of it may approach is to maintain routines in storage for the be requeHted from the computer after each iteration, solution of frequently encountered problems. The Manual retyping of corrected drafts and final text is user specifies the routine and enters data. A fow eliminated. Some 7 e Personnel records •Accounts receivable follow-up e Manufacturing orders 41& Audit correspondence 411 Engineering change orders 9 Acknowledgment letters. G Executive correspondence G Data file maintenance. These examples are by no means exhaustive. Any body of text or data may be more efficiently Typed data can be stored in direct-access stor handled by entering it into a computer for storage, age when it is not being acted upon in core storage. editing, or processing if it is desirable to: Text retrieval would then be simple and the re II) Format sponse fast. Controlled accuracy and increased O Edit production of pre checked form -letter statements •Assemble and tables are ideal for applications such as: e Maintain accuracy ti Price quotations • Make changes over a period of time. • Sales promotions and other form letters 8 IBM 2741 COMMUNICATIONS TERMINAL DESCRIPTION The IBM 2741 Communications Terminal is the • 6 or 8 lines-per-inch vertical spacing (6 lines is combination of an IBM Selectric@typewriter and standard). the necessary control equipment for transmission over a communication line. The control equipment IBM 2741 Keyboard is located in the back of the typewriter stand (see Figure 3). The only control switch that is not part The 27 41 keyboard is physically identical to the of the keyboard is the terminal mode switch. This standard IBM Selectric®typewriter (Figure 3). switch is located on the left side of the typewriter Functionally, one change has been made to the key stand.* board. The Selectric typewriter index key is now The Selectric®typewriter also has the following labeled ATTN (attention).* The indexing(line features: spacing)function is initiated only by the computer. ftlO or 12 characters-per-inch horizontal spacing (10 pitch is standard) *A detailed description of the keyboard controls, 015 1/2-inch paper-width capacity transmission controls, switches, and typewriter CH3-inch-wide writing line with a standard platen paper controls can be found in the IBM 2740/2741 pin-feed platen (available as a special feature) Communications Terminals--Operator's Guide, Form A27 -3001. 9 IBM 2741 PRINCIPLES OF OPERATION General Operation terminal mode switch is set to communicate. The terminal is automatically put in the transmit state The simplicity of operation of the IBM 2741 means and a@ code sent to the computer. The operator that the mrnr need not be trained to use a computer. may transmit by keying as on a typewriter (see Anyone who types can use thi"s device. The user's To Transmit and Receive, in the IBM 2741 Terminal attention is devoted to the content of the material- Operation section of the IBM 2740/2741 Communi not the operation of the machine. The details of cations Terminals--Operator's Guide, Form A27- machine operation are under the control of the com 3001). puter. Simple request sequences are used to spec Terminal transmission ends when the terminal ify the operation desired. The request sequences transmits a @ . The @ is transmitted when the and possible operations are determined by the pro attention key or the carrier return key is operated. gram that controls the computer. However, when the carrier return key is operated, a carrier return code precedes the @ code. The Modes of Operation transmission of the@ code places the terminal in the receive-control state and the keyboard is locked, The 2741 Communicatiorn; Terminal has two modes waiting for a @ code from the computer. of operation: commnnicate mode and local mode. Upon receipt of the@ code, the computer trans The mode of the terminal is controlled by the mits a @ code and the terminal is placed in the terminal mode switch, which is located on the left receive state. Any valid character code received side of the typewriter stand (see Figure :~). from the computer causes printing. At the end of When in local mode, the terminal is disconnected transmission the computer sends a @ code to the from the communication line to the computer. The terminal. terminal can be used for typing, just as any other The receipt of a @ code from the computer causes Selectric typewriter. Nothing can be transmitted the terminal to switch to transmit mode. The key or received. board is unlocked and the terminal automatically When switched to communicate mode, the ter transmits a @ code. minal is initially placed in a control-receive state. Figure 4 shows a typical line-control sequence. The print element is automatically shifted to lower The sequence may be ended only by the terminal. case, if necessary, and the terminal then goes to The operator terminates line control by switching the communicate-transmit state. A @ code is to local mode or by turning the terminal power automatically sent to the computer and the keyboard switch off. Transmissions with the 27 41 terminal unlocks. The operator may now type whatever are not checked for vertical or longitudinal re requests and text are desired. (See To Transmit dnndancy. N.QT.E.: See Code Charts and Keyboard and Heceive, in the IBM 2741 Terminal Operation Arrangements section in this manual for a descrip section of the IBM 2740/2741 Communications tion of the @ and @ codes. Terminals--Operator' s Guide, Form A27-3001. ) Terminal transmission is ended by operating either Programming Considerations the attention key or the carrier return key, both of which cause a@ to be sent to the computer. The operations available to the IBM 27 41 user are The basic indication of the terminal state (trans determined by the program that controls the com mit or receive) is the keyboard. The keyboard is puter. The facilities of the computer may be made locked whcnw1er the terminal is not in transmit available to the 2741 user. Computation, high-speed state. Receive-control Is another momentary speed printing, card pnnching, or magnetic-tape state in which the keyboard is locked and the termi writing of stored information may be included in the nal is waiting for a@ from the computer. Receipt program. of the @ code places the terminal in a receive The computer must be programmed to service state. An automatic lower-case Hhift occurs in the many terminals. As the typist composes (or copies) receive-control state if required. at her own speed, the characters are entered into storage. When information is transmitted t9 the IBM 2741 Line Control terminal, the computer "types" at the maximum speed of the terminal. There must be a method Line control becomes effective on the 27 41 as soon of sandwiching (interleaving) these terminal as the terminal power switch is turned on and the service functions between the time devoted to what- 11 Power Att'n Att'n TERMINAL On @ Key © @Text Cr © @ Text Cr © @Text KEY © MULTIPLEXOR @ Text © @ © @Text © Note: See Code Chart and Keyboard Arrangement section in this manual for a description of the ©and@ codes. Figure 4. IBM 2741 Line Control ever data manipulation is required by the text handling applications; and the PTTC/BCD or application. PTTC/EBCD keyboard and print element, used in The extent of the program is limited by the size on-line computation or programming applications. of tlw computer. A highly developed program for Since the line code assignments of the graphics publishing, for example, might accept rough drafts, used with the standard Selectric typewriter keyboard facilitate editing, and finally print out pages with differ from those used with the PTTC /BCD or two colunms, justified margin, page numbers, PTTC/EBCD keyboard, the processor program must rwming feet, and spaces for figures. Another be designed to accept the particular assignments. program might handle engineering specifications, purchase orders, technical manuals, and new Timing Considerations computer programs. The particular printing element being used by The program must allow time for the mechanical the terminal is also of concern to the programmer. functions of the terminal to take place. This is done For instance, on the Courier 72 print element, the by inserting idle codes for the time required. Any digit 1 and the ±.symbol replace the J and the [ code which is ignored by the terminal may be used. respectively on the Manifold 72 element. One ap Common practice is to use the BCD idle code proach to this situation is to define a change-of (B8421). print-element code sequence in which the operator The number of idle codes required for each informs the computer of the print element being mechanical operation is as follows, where N is the used. number of idle codes required, and T is the number of inches of carrier travel; round off the result to Keyboard Considerations the next higher whole number. Carrier return: N = T + 1. 5 The type of keyboard and print element to be used on Tab: N = T + 1. 5 the 2741 terminal typewriter can be specified when Index: N = 1 the terminal is ordered. The types available are If the program uses the opportunity to transmit the standard Selectric® typewriter (correspondence) when offered by the @ that follows each carr~er re keyboard and print element, used primarily for turn, time must be allowed for the carrier return to be completed before transmission begins. 12 Page of GA24-3415-2 Revised Feb. 3, 1970 By TNL: GN27-3053 SPECIAL FEATURES Typamatic Keys Data printed on the line during which the interrupt occurs may not be identical to the data transmitted The Typamatic keys are the space bar, backspace to the CPU. For this reason, the interrupt should be key, and hyphen/underscore key. If one of these eonsidercd a terminating condition that voids the en keys is operated normally, the corresponding func tire line. tion occurs once. If the key is pressed and held, the Communications facilities for 274l's using action is repeated until the key is released. Transmit Interrupt must have duplex capability (simultaneous two-way transmission). Receive Interrupt Print Inhibit The Receive Interrupt feature allows the 27 41 oper ator to interrupt computer transmission. If this The Print Inhibit feature enables the CPU to in feature is installed, the Attention key is active when hibit printing at the 2741. A bypass code (A 8 4) the terminal is receiving text. The operator presses received by the 2741 initiates the inhibiting func the Attention key to cause an interrupt. This causes tion. When in the print inhibit mode, all print the 2741 to transmit a 200 to 3GOms continuous space able characters received or keyed at the 27 41 are signal. This signal requests that the computer pro recognized and cause the print element to function, gram end transmission by transmitting a The © . but no printing takes place. program may or may not honor this request. If Printing is inhibited until a restore code (B 8 4) transmitted by the CPU, the places the 2741 in © is received to reset the inhibiting function. The transmit mode. The terminal then transmits a @ print inhibit function is also reset by a power-on and its keyboard unlocks. sequence. Data printed on the line during which the interrupt occurs may not be identical to the data transmitted from the CPU. For this reason, the interrupt Dial Up should be considered a terminating condition that voids the entire print line. The Dial-Up feature allows the 2711 to be attached Communications facilities for 2741 's using Re to a common-carrier switched network. A \Vestern ceive Interrupt must have duplex capability (simulta Electric Data Set 103Al or lO::lA2 (or equivalent) is neous two-way transmission). required to attach the terminal to the eomrnon carricr switched network. To establish conneetion with the computer, the Transmit Interrupt terminal operator places the data set in talk mode, dials the telephone number of the computer in the The Transmit Interrupt feature allows the computer conventional manner, listens for an answer tone to interrupt 2741 transmission. To interrupt, the from the computer, then places the data set in the CPU transmits a continuous space signal. The dura data mode. The connection is terminated either by tion of the space signal is set by the CPI; program turning terminal power off, or by returning the mer in increments of a character time and must be data set to talk mode. a minimum of three character times (more than 200ms). (A minimum of one character time of mark signal, transmitted automatically by the IBM 2702 or Pin-Feed Platens 2703, must follow the space signal.) Reception of the space signal causes the 2741 to change to receive Pin-feed platens are available in the following inch control mode and await a @ or from the CPU. © sizes to replaee the standard friction-feed platen NOTE: An inteTI'upt signal received by a 2741 which is not in on the IBM 2741 Communication Terminal Selectric transmit mode causes unpredictable results. Typewriter: 13 Page of GA24-3415-2 Revised Feb. 3, 1970 By TNL: GN27-3053 Overall Forms Hole-to-Hole Writing modulation and demodulation for transmission on Width Width Line two-wire or four-wire communications lines up to 4. 75 miles In length with a single 2741 attached. Two versions of this line adapter are available: 5 3/4 5 l/4 4 3/4* Type lA for two-wire systems, and Type lB for 6 1/2 6 5 1/2 four-wire systems. 8 7 1/2 7 8 8 7 1/2 IBM Line Adapte1~ (Limited Distance Type 2) 9 1/2 9 8 1/2 9 7/8 9 3/8 8 7 /8* This feature permits the customer to attach an 10 3/8 9 7/8 9 3/8* IBM 27,1.1 Terminal to customer-installed commu- 10 10 9 nications lines or leased comrnon-carrier private 10 10 1/8 9 5/8 line ehannels. The line adapter feature (installed 11 11 1/4 10 3/4 within the 27 41) provides the necessary signal 12 11 1/2 11 modulation and demodulation for transmission on 13 12 1/2 11 7/8 two-wire communications lines up to 8. 0 miles in J)l 13 1/8 12 5/8 J ength. 14 1:3 7 /8 13 1BM_!::_i_ne_~da1~ter (Leased Line) ·*!\ vailable in ,;x Iines-per-ind1 only This feature permits the customer to attach an IBlVI Continuous forms used with pin-feed 2'741 Terminal to a leased common-carrier private should be stapled, g;lmxl, or stitched. The line or equivalent privately owned number of copies that can be o«ucHa'" line adapter feature (.installed within the pro depends on paper and carbon thickness, and on the vides the necessary modulation and dernod- height from which the .forrns arc fed. A maximum ulation for transmission on a con1nmnications line of rm original and four copies can he without length restriction. IBM Line C OJW.M UNICATIONS C ONSIDE HA TIO NS - " __ ,. ------Thjs feature permits tho customer to attach an IBM 2741 Terminal to one of four subchannels which The IBM 2741 Communications Termillal communi- can be obtained from either the customer's privately cates with Uw computer (multiplexor) on either owned or leased common-carrier telephone-grade privately owned or leased common-carrier commu - communications facUHies. This line adapter also nications facilities. One commun lcations line is provides the necessary signal modulation and required for connecting each 274,1 to the rnultiplexor. demoduJation required for data comrnun.ications. With this feature, one telephone line can provide up to four separate paths for simultaneous data trans - mission. 1'his line adapter is available for opcr This feature permits the customer to attach an ati.on on either two--wire or four-wire communications IBM 27/H Terminal to customer-installed commu facilities. NOTE: For additional information on the nications lines or leased comrnon-carrier private use of IBM line adapters, see Plal_!!ling and Instal line channels. The line adapter feature (installed lation of a Data Communications System Using within the 2741) provides the necessary signal IBM Line Adapters, Form A24-3'135. 14 CODE CHAHTS AND KEYBOARD ARRANGEMENTS Figures 5 and 6 illustrate the standard IBM Selectric typewriter print element (see Note- Selectric®typewriter keyboard arrangement and Figure 5). corresponding tramnnission codes employed when The line code-assignments for the two line control the terminal is used for normal correspondence codes used vvith the 2741 are (C 8421) for the EOT and text type operations. Additional keyboard @ and (821) for the@ . The@ code is unique arrangements and print elements are available and has no graphic associated with it. The @ , on that provide compatibility with the PTTC/BCD and the other hand, has the same line code assignment PTTC/EBCD codes. These keyboard arrangements as the digit 9 (lower case) and left parenthesis and codes are normally used in time-sharing appli (upper case) on the standard Selectric typewriter cations. The PTTC/BCD and PTTC/EBCD code keyboard arrangement. Its corresponding graphics charts and corresponding standard keyboard arrange on the PTTC/BCD and PTTC/EBCD keyboard ments are shown in Figures 7, 8, 9, and 10. The arrangements depend upon the code and character choice of keyboard must be made when the 27 41 is set used (see Figures 8 and 10). The (821) code ordered. Although the PTTC/BCD and PTTC/EBCD will print only when received or transmitted in the print elements are interchangeable with each other, text mode, and not when used as a line control they are not interchangeable with the standard character. OFF SET [E3][][;][]0GJGJGJDDWI~lsHl~FTI I SPACE BAR I Note: When this keyboard and associated prird elements are specified the mechanical changes in the keyboard mechanism determine the line code assignments of the graphic charocters. These arrangements are not compatible with the assignments provided by the use of the PTTC/BCD and PTTC/EBCD keyboards and associated print elements (see Code Chart, Figure 6). Figure 5. Keyboard (Standard Selectric Typewriter) 15 Bit Va!ue LOWER CASE UPPER CASE _1[_]_ - ·-·-·--·-4--···-·-- 2 -frlE CODES BELOW ARE HOT PRIHTABLE Fl!~~C T!Ot'-l CODts *See Code Charts and Keyboard Arrongtm1ents aectk>n in this f"10nvol. Figure 6. L.ine Code Chart (Standard Selectric Typewriter Print Element) 16 fMAR1 ~ nn 1%1CJ~~rnm1-11+1 BACK ~ [Jr:l 6 SPACE ~ WL2JW~~ L2J~L?.J~LJ~ ~ CLR TAB GG0D~~G800[1] 0 ON EIJGJGJ~EJ~000QOJITJD SET [}3JGJGJ~GGJGEJ[JDQJ.---.--IlsH~inl I OFF I SPACE BAR I Figure 7. Keyboard (PTTC/BCD) 17 LOWER CASE UPPER CASE CHARACTER CHARACTER SET Bit Value SET Std. I A I H I Typ. B I A I c I I 4 I I Std. A I H Typ. A I c A c i----;y· I I + ... ·,i· I I 1/2 A 6 1/4 & + A c < + !---· I I A c " > ! I @ c --~ 4 b $ 5 c 4 % I ( % ~--····-·····-----1------+-~--'---l---j 6 c ~ & --·-·------·--~·--·------1--~-~-~~--1 9 c [ c J A A A A c c A D A c A 4 F A 4 G i--.-... ------~------+------A H ~,·~---·------+------+--··------A C I ·-·--i------l------c--·------ie-----J------k C --·--2-- K ------!- -··---·------.. ------.. ------·-·------~------B 2 l L ----"---··-----·--z----··--··-.------~----M-·-·-·-·- ,..--...... ··-·- B 4 1 N ------~------···---~------.----·-----~-----·------_____ ,,__ ,______o ------.B 4 ------>------2 0 p B C 4 2 1 P c Q ------·------~------+------l ------+----- A ______s:___,, ______!~-----L-...... ·------' A 2 I ------·- -~ -----·--·---·--·-- ---~-~---~------v A C 4 u f------· ------·-----·------A-.------·:(______------v ------·------A------~------~-- -·--- -w-·------ ---·------~--·--A--c------4·-----2-----1------x---·- ------,------.. --~------··- A C 8 Y ------! A z THE CODES BELOW ARE NOT PRINTABLE r------' FUNCTION CODES MEANING 0 0 =-·------c:oc~·-,-S------11--B---- :--~-~-=~~~--:------__ -_-_ --1-1--_ ---_ -_ -_ 7-::-~-,:-~e-.------I t---·-- +------PF B A C 8 Punch Off ___R_s ______+------______!_~ ~--R_e_o_de_,_s_t_oP______, i.----~---·-L_F ..------1- A C 4 ______]__.L. Line Feed------·-----1 NL C ---~---4-----~--~· New line (Carrier Return and line Feed) HT A 8 4 1 Horizontal Tab ------+------··------~--·------< UC 8 4 Upper Case ~----- .EOB____ --- .. - ~----A··--c--B--4-- End of Block ------!------' ~~------~·-·------c:______------1-----·--B-ac_k_spc..a_c_e______, LC B A 8 lower Case 1------,, ______------.------·------! kEOT C 8 4 2 1 End of Transmission ~----PRE.. -·---··-·------A -s--:i---2--~-~---P~~fix______, 1------.------~------e------.------+- IL B 8 Idle ~---DEL------___ .__B______A ______C ____ a_ ------'----D-e-le-te______, ------~·------·---- Space c Space *See Code Charts and Keyboard Arrangements section in this manual. Figure 8. Line Code Chart (PTTC/BCD) 18 Figure 9. Keyboard (PTTC/EBCD) 19 Bit Value ~ LOWER CASE _!_~_J_::__ I I 4 I I UPPER CASE B A c r-· A c *# @ A & A c >---·---· I A c 1 0------2 < c 4 ------c--~~4-·-·-·------'------o/,-,----' c 4 > r;----,---··------>--·---·------+------l8 ______9 ______~ ______c______. ______, c 2 A 1 A i------1-----A ·------+----~~---~B ,______,__ ,c -----+------!------< A C C d A D ------+---- __ •,, ______,___.B ______A c _,______, f B A C F -- g __B_____ A ___·----·-----··-··· G h B A 8 H __ ,,,. ____ ,,, ______~---·~------,------>--·----~------A C J I i B C 1--~----y-- ...... ~---~------~~·--.--·---·-·-----·------·------+---·--·-·-----·------·-1------C K 1 B 2 I L -·------f------··---·--- ···----·-~--~-·-~-- B C 4 M ------.---,·~-···--·------.. •--••••••V·--·--·-•·--·-·------·-·- ~------' B 4 1 N -----·-----~-~------0 ~----.-- -~-·---~·--_e______,______c_ ------.. - .. --·------~--~------c Q ~-----+------~--~------>------! ------·------·------·-----! A l -·-----+------···-···· ·------···--+------! u A C 4 U ···---v------+--·-·-----A---- ·-----4-----··-1--·----v----- l---·-···---·-·-··------1-·------·· ·- -·-·------'~----·----~ A --·-·----~------w_' __ ------·-+------AA ___ Cc_____ s______2 +-----Y-.--·- X y z A B l Z THE cnriEs RFI ow ARE NOT PRINTARI F FUNCTION CODES MEANING f------~ :~ ~§-;- __c_ ~--:--~------~____ ·_-_-_·-· __ -'::"":_:_~'-o_"______.__ . ., _ __, __ _ _ -~E~--- ______8 4 ------·---+------R_e_,_1_0,_e______:.c __ __, Pf B A C 8 4 Punch Off .. ------~ .. ---·-----~---~------+-----·------''---! RS 8 4 Reader Stop , ... f------~-,-·-r------·------·------··---+- ______.:.. ______;;. __ -! A c 1 Line feed ·- ----·-·----~------_l_--... --·------< NL B C 8 4 l New line (Cartier Return ond Line Feed) _____H_T _____ B ______A __ ,, _____8--4· -----<------H-oc-;z_o_n_to_lc_T_o_b------~ r-~---·------·------+-·------·------·------,-··----·+------! UC 8 4 2 Uppec Cme ---~----·------!------· ------.. -·------+------'-'------! EOB A C 4 End of Block ~-----· .. -~------+------>--·-----'-'C------1 BS C Backspace f----·------·----~ LC B A 8 2 Lower Case ------:-Eor-··---··---~~----·c-----8-4--2------End of Transmission ~----·PRE----~--·-.f-.-·---- A 8 4-·-·-----·-2-- ·--,-i-- Prefix .,. f------~---·-----·------~----- IL B 2 1 Idle 1-----~------J-----·------DEL B A C Delete ·------~"------~ Space c Space ~-~~~~--~~'---~~-~~~~-~~~~~---~--'-~~--~~~~~~~~~~~~~~--" *See Code Charts ond Keyboard Arrangements section in th ls manual. Figure 10. Line Code Chart (PTTC/EBCD) 20 GLOSSARY OF TERMS Some of the terms used in the data processing and Modulation: the conversion of digital signals from communications fields have specialized meanings. a business machine to audio-frequency signals The following definitions may be useful. for transmission over communications lines. Data Set: a modulation/demodulation device de Non-switched line: a communications line devoted signed to provide compatibility between input/output to one user, that is, not part of a switched network; equipment and communications facilities. a leased private line or privately owned line. Demodulation: the conversion of audio-frequency On Line: associated with a processor either signals from a communications line to digital directly or through a transmission control unit. signals for a business machine. The physical connection can be accomplished by either multiwire cable or a communications line. Direct-access storage: in data processing, a storage medium for data in which the data is avail Program: the series of instructions, meaningful able for immediate retrieval, that is, not serial for a computer's control unit, that define, step access storage. by step, the operation of the computer for the solution of a given problem. Full-duplex: a communication channel capable of transmitting in both directions simultaneously. Switched Line: a communication line used by more than one user (customer); part of a switched network. Half-duplex: a communication channel capable of transmitting in both directions, but in only one Terminal: a machine or group of machines capable direction at a time. of generating and/or receiving signals to be trans mitted on and/or received from a communications Modem: another name for data set. line. 21 GA24-3415-2 0 0 3 3 c "' ;!; 5"' :J -I 3"' ~ International Business Machines Corporation Data Prm:essing Division 112 East Post Road, White Plains, N.Y 10601 [USA Only] IBM World Trade Corporation 821 United Nations Plaza, New York, New York 10017 [International] READER~COMMENTFORM IBM 2741 Communication Terminal GA24-3415-2 • How did you use this publication? 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E01 ::j -cl I 6 - --~ ~ Fold Fold I ~ ...::J "'CL ::J c (n )> G) )> N w-!> -!> 01 N ® International Business Machines Corporation Data Processing Division 112 East Post Hoad1 White Plains1 N.Y. 10601 [USA Only] IBM World Trade Corporation 821 United Nations Plaza, New York, New York 10017 [International] A24-3415-2 Internaticmal Business Machines C:orparation Data Processing Division 112 East Post Raad, White Plains, N.Y. 10601 [USA Only] IBM World Trade Corporation 821 United Nations Plaza, New Yark, New York 10017 [International]