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Text File | 1992-02-08 | 18.9 KB | 520 lines

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It's a process loaded with the need for patience and persistence. However, "No pain, no gain!" Computer telecommunications is the process of hooking two <GLOSSARY 6 5> computers together through a telephone line to exchange files of information and programs or carry on live conversations. Your computer will need a device called a MODEM which allows data to be converted into a special <GLOSSARY 15 18> signal which can be transmitted over a phone line to another computer. There are two types of modems: ┌──────────┐ ┌──────────┐ │ Internal │ and │ External │ └──────────┘ └──────────┘ External modems are a bit more expensive than internal modems because they have their own case and power supply. External modems require a socket on the computer or port (usually the serial port on the back of your computer.) The serial port is also called a COM port, com for communications. Most PC's come with a serial port, a few must have it installed. If you are already using the serial port for something else SERIAL DATA like a mouse or joy stick) you may need an additional port <RS232> installed. You may be able to temporarily unplug the device SERIAL PORT using the serial port. External modems take up a bit more <GLOSSARY 22 11> space and add a bit more clutter on your desk (internal modems are installed inside the computer.) Some people like the external modem with its blinking lights which instantly displays the call status. Another consideration is that external modems are portable and can be moved from machine to machine by simply unplugging the modem. DEFINITIONS The "host computer" is the one your PC is calling. Sometimes this is a commercial service such as Delphi, GEnie, Prodigy, or Compuserve which are large interactive services. Other times the host may be another PC your friend is using on the other side of town or perhaps a bulletin board system (BBS) which is a computer operated for general public access by a private individual or company with files and messages of general public interest and access. Another important term is baud rate. It is associated with the modem transmission process. Baud is a reference to the speed at which your modem and the host modem exchange information. Some common rates are 300 baud, 1200 baud and BAUD 2400 baud. You should obtain the fastest baud rate modem you <GLOSSARY 4 2> can afford. Most BBS systems will not even let you connect at 300 baud any more. A 1200 baud modem is roughly 4 times faster than a 300 baud MODEM SPECS modem. Since you may be transmitting information long <MSPECS> distances, speed, and brevity of the modem link can really be an important factor. HAYES COMMAND SET As an aside, a 2400 baud modem can be switched to transmit <1200> and receive at the slower 1200 and 300 baud rates so there <2400> is some "downward" flexibility in purchasing a high speed modem which allows lower baud rates as needed. The software which controls the modems, and computers linking during the exchange will "synchronize" the two modems, determine which modem is using the slower speed and adjust the faster modem downward to that speed. Many BBS systems use the 2400 baud rate and some are even capable of 9600, 14,400, or even 38,800 baud - in this case the BBS host computer will slow to your rate. If you plan to do much long distance modem work, a 2400 baud modem, or faster, is the wisest choice. The higher purchase price which will be offset by savings in reduced long distance rates. Next, take a look at the communications software. While DOS TELIX IS THE controls the internal workings of your computer, you'll need BEST! communications software to enable the PC, modem, and telephone line to work together. Many "integrated" commercial software packages have a communications package built in or added as a separate module. Shareware and public domain packages also exist. Some of the more dependable software packages include: ░░░░░░░░░░░ ┌────────┐░ │ │░ │ Qmodem │░░░░░░ │ ├────┐░ └───┬────┘ │░ │ Procomm │░░░░ │ ├──┐░ └────┬────┘ │░ │ Boyan │░░░░░ │ ╞═══╗░ └───╥───┘ ║░ ║ Telix ║░ ║ ║░ ╚═══════╝ ░░░░░░░ ┌─────┐░ │ and │░ ░░░░░░░░░░░░░░░░ └─────┘ ┌──────────────┐░ │ │░ │ GTPowercomm │░ │ │ └──────────────┘ Good communications software is flexible and powerful TELIX IS without being hard to use. The best comm programs have help THE BEST! screens and tutorials. Telix, for example asks a few simple setup questions then attempts to set the numerical settings needed without operator intervention or frustration. Although obscure at first, the modem software setup process allows you to configure the software package for your specific PC and modem combination. The modem software needs to be told which serial port (COM port...usually 1 or 2) you will be using. You will need to tell the software which directory or drive where files will be sent (downloaded). The baud rate must be set. You will usually have to tell if the modem is Hayes compatible. Hayes compatibility refers to a standard set of transmission instructions which many modems share. A very good program for Telix users to get is T-FIG, The Telix Tutor. This program is designed for beginners. It actually reads the Telix comm program's configuration and displays it in screens of text explaining what the items are, what they do, and what they need to be. * T-FIG is available from the author of this program. Other basic details like PARITY, and DATA BITS have to be <PARITY> set. These refer to how the data is "grouped or packaged" during the actual modem transmission. Generally data bits DATA BIT(S) are set to 8. Parity is usually set to NO. Commercial <GLOSSARY 8 22> services such Compuserve offer exception to these settings and will tell you these settings in their literature. An example: If parity is required, set data bits to 7. Set stop STOP BIT bit to 1. This is a total of 1 + 7 = 8 Bits. The <GLOSSARY 23 17> final bit is usually used to check parity/accuracy. The above setting is cryptically referred to as 8N1 START BIT which means 8 bits, no parity, one stop bit. Don't <GLOSSARY 23 14> worry about this too much. Often this is a one time setup. Once its done you can forget it. Other settings can include ANSI standard terminal emulation ANSI (a standard selection you should check if given the choice). <GLOSSARY 1 9> ANSI terminal emulation is usually the default setting and should only rarely be changed. PROTOCOLS will have to be specified. The protocol is a PROTOCOL method of checking for errors between modems as the data <GLOSSARY 20 1> transmission progresses. In a precise fashion, these protocols tell the first modem to transmit a small packet of XMODEM data . . . then the receiving modem will play back a short <GLOSSARY 28 11> verifcation "checksum" or "password." The transmitting modem stops, listens for the checksum and if it matches the YMODEM information which was sent, the first modem transmits the <GLOSSARY 29 9> next packet of the message. This continues, one small packet of information/data at a time. The idea is to protect data ZMODEM integrity over noisy, static-prone telephone lines. <GLOSSARY 29 12> You need a protocol for sending (uploading) or receiving (downloading) data. Several common protocols include Xmodem, Ymodem, Xmodem-CRC, and Zmodem. Xmodem is generally offered by most BBS systems and is a safe bet when you are not sure what to use. Other protocols are somewhat faster and/or slightly more dependable, but Xmodem will do the job. Trial and error or simply logging onto the BBS system with Xmodem and then inspecting the menu of other protocols available will give you more detailed information and clues about other possible protocols. Ymodem offers a faster transmission rate than Xmodem, better data security through a refined CRC checksum method and finally a method for "batching" or sending/receiving several files one after another unattended. Zmodem is faster still, somewhat more secure with respect to data loss, likewise offers batch transmission of many files and additionally allows a file to be partially stored if the PARTIAL TRANSFER connection is lost and then completed when the connection is <GLOSSARY 29 15> restablished so you do not have to transmit the entire file again! General considerations in selecting software for modem use include: * The dialing directory is REALLY important. The idea is that the package will store and dial your most frequently dialed numbers. Some packages hold only a few, some quite a lot! Does the package store your individual password and comments next to each number? What about linked scripts that will run whenever a specific online connection is made? You may wish to use different passwords for each BBS system you call. * Transfer protocols offered. Xmodem is a basic, but you may want more efficient protocols later. Make sure the package supports several or can be upgraded to more protocols later. Zmodem one is the best. * How are numbers dialed from the list? Will the program call back and continue trying if the number is busy? Can it dial numbers from the list in a certain order. Can it do circular dialing (several numbers are called in a row, then the program jumps from the bottom of the list and starts at the beginning again - around and around in a circle)? This type of dialing is important if you deal with busy communications services and BBS systems where it may take time and several calling attempts before logging on to a system especially during the busy evening peak time. * Does the package offer scripts or macros? A script is a way of having the package automate several steps. Without further input the package can call a BBS system, type in your name and password and then continue typing further keystrokes as if you were entering them from the keyboard yourself. Script capability is a programming-like language which gives the communications software package a customized way to enter many keystrokes while you only input one or two strokes to start the process. Many programs let you even record the sequence of keystrokes during a communications session for playback and retrieval later. Beware though, if the system which you are calling changes log on sequences. You may have to go back and later revise your original script. Not a major problem, but sometimes it can be a hassle. * Does the program allow you to capture screen information to your disk drive? Can you send screen information to your printer? Long communication sessions on line with your modem produce endless screens of information which scroll by quickly. The ability of your software package to output all or selected parts of your session to permanent disk file or printer output can be a definite bonus. Local neighborhood BBS systems can offer the most entertainment and information for the first time user. The principal rule of behavior: "Act like you are in a good friend's home." Courteous behavior is a must. How do you find telephone numbers for these systems? Consult local computer clubs for a few numbers for BBS systems and then call the BBS systems with your modem for lists of MORE local telephone numbers. BBS operators and users are quick to answer questions for new users and can serve as helpful "experts" on any computer question. Operators of these BBS systems are frequently called Sysops and many provide BBS systems as a hobby activity much as other hobbyists enjoy short wave radio operation. Most BBS systems will allow you to tour within the various activities and parts of the system for 30 minutes to an hour on your first call. After that you are expected by some "boards" to leave your name and a phone number where you can be reached for verification. Some boards are free, some request a nominal use fee (usually around $25 per year.) Some boards request that you upload (send to them via modem) shareware files or public domain software in order to download their software. The process is something like two kids with baseball trading cards: "I'll trade you 225,000 bytes of this shareware file for 250,000 bytes of your files." You usually are allowed access only to certain "low level" (but interesting) areas of the BBS "board" on your first visit. The Sysop (system operator) may be available to come "online" if you experience difficulty. The software of the BBS system itself will safely keep you from damaging the host computer even if you hit an incorrect key or enter a wrong command. You may leave messages for the Sysop, leave messages of a general nature, ask for help on a specific question, download public domain software, play a game, or just generally explore the information within the system of the host computer. Downloading files is easy. For many boards the command is a simple "D" for download. The BBS will ask you the name of the file you wish to download and then give you an estimate of how long it will take and the modem protocol you will (or should) be using. After that you key in a keystroke or combination which tells the software in your computer to begin the process. When the transfer is complete, the host BBS takes over and presents the main menu of choices or selections. Lists of phone numbers for online services and BBS numbers are available from most of the boards themselves, local computer club newsletters, and many computer store salespersons. Most public domain and shareware software from BBS systems SHAREWARE is stored and transmitted in a compacted form called an <GLOSSARY 22 20> archive (ARC, ZIP. PAK, or LZH format). You will need a small public domain or shareware program also available from the BBS board to unarchive (unpack) the software. This archiving process is done to compact the software for shorter, more efficient transmission. It saves time and disk space for both the BBS and you. The easiest way to visualize arc'd or zip'd software is to think of the many files of a typical software package compacted in size and then placed into one single file. You might also wish to compact your other files for storage on a hard drive aside from the modem process. File compaction is a useful tool all by itself! PKARC, PKZIP, PAK, and LHARC software are shareware packages available from BBS systems. Working with modems and telecommunications software sounds mysterious and intimidating at first. However, it is a thoroughly enjoyable and rewarding hobby. It's also a nice way to make friends and explore more deeply the global network of information and friendships.