Magnetic Pages Article | 1993-10-14 | 31KB | 236 lines
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[30;41m ABOUT MODEMS and BBS
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[3;2m By Kenneth Bartrum
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[3;2m July 1993
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[1;33m Distribution Notice:
B This article may be freely distributed in the Public Domain byD electronic bulletin board, or commercial on-line service, and/orE PD library, subject to the following provisions that neither thisE Distribution Notice nor the following article shall not be editedB or changed in any way for redistribution, and provided furtherD that no charge is made for any copying of this material over andB above the cost usually associated with the medium by which the
B This article remains the property of the Author and may not beA reproduced other than as authorised above without the written2 permission of the Author being first obtained.
E
[1mAmiga
[0m is the registered Trademark of Commodore-Amiga Inc.
[1;33m Disclaimer
D While every effort has been made to provide information valid atD the time of publication; information contained herein is subjectD to change without notice and the author shall not be responsibleC or be held liable for any damage caused by error, ommission, or% misuse of the information herein.
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[0m - use 10-pitch (12 characters per inch) 6 lines per inch,7 single spaced font such as Courier, Pica, or Elite.
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[30;41m What You Need To Know About Modems
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E Although aimed at the Amiga User audience, the information hereinD may be useful to anyone interested in high-speed modems (or 2400E bps modems with MNP-5 or V.42bis). Most modems mentioned in thisG article are external units and can be used on any Personal Computer, system, be it an IBM, Mac, or Amiga, PC.
D This article will provide interesting and informative reading toG both the new user and to those of us who know a little about modemsG and the advantages they bring when on-line with your favourite BBS.
[1;33m Did I hear someone say, what's a BBS ?
F No, - BBS is not some rude expletive. BBS is the abbreviation forF a Bulletin Board Service usually provided by some dedicated personG offering the means through which information, user help data files,F games, and electronic mail, can be accessed. The various functionsE of a BBS go much wider than those I mention here as any user of a
BBS soon discovers.
[1;33m The World of BBS
F It is estimated that more than 50,000 bulletin boards exist in theF United States. How many BBS's there are operating in New Zealand ID do not know. No matter where you live, you will probably find aF local BBS carrying some Amiga support. Most BBS operate as a hobbyG by their owners. Some with and some without charge to their users.5 If you are a Sysop, please write and let me know.
D The world of BBS is no longer restricted to isolated systems forC local use only. Fidonet, is a network linking thousands of BBSE around the world; and through Fidonet users on one BBS can easilyE communicate with those on other BBS anywhere in the world. UsenetG is another, and Compuserve possibly the largest commercial service.F Recently, with gateways to the UUCP network, many BBS have allowedF their members to exchange e-mail with users of the Internet and to% participate in Usenet newsgroups.
[1;33m What role does the Modem play
F The most important tool for users wanting to know more about goingE on-line to access any BBS is the Modem. So called because of itsE function and stands for MOdulator/DEModulator; converting digitalC signals generated by the computer into analog signals which areD transmitted over a telephone line and transforms incoming analogF signals into their digital equivalents. Don't let the language ofE technology put you off. You need concern yourself with technicalD knowledge only on a need to know basis, and then if and when you% install a modem and access a BBS.
L Nevertheless some basic knowledge
[3mAbout Modems and BBS
[0m is a mustE before you make the committment financially. There have been manyE changes in the price of modems that reflect their suitability forA whatever your particular need may be. But more on this later.
[1;33m First things first
E Before you can access a BBS you must first have your Modem up andD running with a suitable communication software package installedG in your system. The communication software programs NComm, JRComm,B and TERM, are among the most common and are available from anyF reputable Public Domain Library or through most Amiga user groups.D X-Comm - a very powerful shareware comms package was released inG January 1993 and is attracting considerable attention. Please write0 to me if you want more details about X-Comm.
[1;33m Shopping around
E The cost of many brand named Modems available in New Zealand have; fallen to a level where they are now more 'affordable'.G A 2400 bps modem can be purchased from under $200, and a 14,400 bpsD fax modem for under $700, retail in NZ. But check out the brandH against its cost/performance and make sure it will do what you want.
E If you don't have a need for the 'fax' component, check the priceF for the same brand without the fax component. Also check that theG price offered is inclusive of the operating software and whether orD not the price includes the interface cables. The all up cost isE what you want to know before you commit yourself to any purchase.
G Remember! There are horses for courses, and modems more suited forH specific needs, all with different protocols. Be careful, and don'tF be rushed into something that may be cheap at the initial purchaseD but costly in terms of download connection time. Watch also for
backup support.
K
[1mPlease don't
[0m be tempted to buy into a 1200 bps modem; they areE outdated and no longer in demand. I had a distributor offer me aF deal to practically give them away just to get them off his shelf.B But seriously, 1200 bps modems have had their day and are fast
becoming museum pieces.
H
[1mPlease do
[0m check out the BBS that you may be connecting with.G Most BBS services still offer a 2400 bps baud connection as the lowE end entry level. The number of BBS services offering a 14,400 bpsF connection is on the increase. One main advantage is that most ofE the 14,400 bps modems step down and connect to 12000, 9600, 4800,
2400, and 1200 bps modems.
E Buying and using a modem used to be relatively easy. Not so longF ago, almost all modems were 1200 or 2400 bps units compatible withG the Hayes Smartmodems (some are more Hayes-compatible than others).
Now it's a new ball game.
G Todays modems not only have much faster transfer rates, run faster,G and are also loaded with features that take the misery out of errorG control and data compression. Suddenly, you are confronted with allC the buzzwords: V.32, V.32bis, V.42, V.42bis, MNP-5, LAP-M, etc.F Now you know why I said earlier, don't get put off by the languageG of technology. Don't worry about what it all means until you 'needE to know'. The important thing for users new to modems and BBS isF that you feel comfortable with the knowledge you pick up and learn
on a 'need to know' basis.
F Your local Amiga user group will almost certainly have members whoG can and will help you with discussions about modems. Your local BBSG Sysop (Systems Operator) will also be helpful and is well worth the
contact.
[1;33m 2400 bps Modems
F A 2400 bps Hayes-compatible modem typically supports the following
modulation protocols:
2 Bell 103 ( 300 bps U.S. Standard)2 Bell 212A (1200 bps U.S. Standard)C CCITT V.22 (1200 bps standard used outside the U.S.); CCITT V.22bis (2400 bps International Standard)
C Some 2400 bps modems also support the following protocols:
B CCITT V.21 (300 bps standard used outside the U.S.)C CCITT V.23 (1200/75 and 75/1200 bps, used in Europe)
F "CCITT" is an international telecommunications standards committeeF that makes recommendations on a broad range of subjects concerning
data communications.
D Some low cost 2400 bps modems do not support error correction orC data compression protocols. Recently, some modem manufacturersB introduced 2400 bps modems with extra features supporting dataF compression, error correction and fax capability. So if you are inE the market place, a little knowledge can help you better evaluateF what the salesman is telling you. Moreso, what the salesman is notF telling you. The key is to know enough to ask the right questions.
[1;33m High-Speed modems
F Modems that feature modulation protocols at 9600 bps or higher areF regarded as the entry level for high-speed modems. If you are toldC a 2400 bps modem with data compression performs as a high-speedF modem, you can be sure that information is wrong. A 2400 bps modemF that is said to theoretically yield a 9600 bps throughput is not aF high-speed modem. Why? Because it is the raw speed, without dataE compression, determined by the modulation protocols that generate
the true high-speed modem.
E With all 2400 bps modems the single modulation protocol (V.22bis)D was supported by modem makers. Now there are several proprietaryE modulation protocols used by modems from different manufacturers.F They come with default settings pre-configured at the factory withC V.32 high-speed preset to use V.42bis and hardware flow controlD when turned on. This optimal configuration enables the automaticC connection with either another V.32 modem supporting V.42bis or- MNP protocols (or even a standard modem).
O
[1mV.32
[0m was the standard for 9600 (and 4800) bps modems adopted by the
CCITT in 1984.
R
[1mV.32bis
[0m is the CCITT standard established in early 1991 for 14,400 bpsF modems. All V.32bis modems can fall back to 12000, 9600, 7200 andB 4800 bps. And V.32bis is also downwardly compatible with V.32.
[1;33m Buying a High-speed Modem
B V.32bis modems are the standard of high-speed modems today andB unless your application requires a high-speed modem supportingC a proprietary modulation protocol, you would be well advised toB buy a V.32 or a V.32bis modem. A dual-mode modem that supportC both the proprietary protocol and V.32 (or V.32bis) would be my
preference.
C V.32bis modems are faster than V.32 modems but they costs more.C Should you pay the extra for the speed difference? That dependsD on two factors: what's the price difference and how do you want> to reach the system at the other end, (the remote system).B If the price difference is $50, I would buy the V.32bis modem.. But what if the price difference was $200?
D Assuming the remote system support V.32bis, a V.32bis modem willB pay for itself rather quickly if you are placing long distanceF calls to the remote system. However, it may be more cost-effectiveE for you to use some packet-switching networks to reach the remoteE system by calling a local number. A V.32bis modem will be wastedA since none of the packet-switching networks currently supportE V.32bis. In fact, they are just starting to offer 9600 bps accessE service. The technology of packet-switching networks is again onB a 'need to know' basis, if, and when, you become familiar with
modems and BBS.
[1;33m Should you buy a 2400 bps modem with V.42bis?
C If you are thinking of purchasing a 2400 bps modem with V.42bis" data compression, think again.
C V.42bis and MNP-5 are useless for downloading compressed files.E There is one more reason why a 2400 bps with V.42bis is generallyF not useful when you are calling commercial online services or BBS.
C Online services and BBS usually have separate phone numbers forG 2400 bps and high-speed modems. Most of them do not support V.42bisD on their 2400 bps lines. Therefore, you won't be able to make aC connection with V.42bis if you call their 2400 bps modem lines.
? Couldn't you call their 9600 bps lines? Well, not really.G Commercial online services, as well as many bulletin board systems,C typically do not allow you to call their high-speed modem linesF with a 2400 bps modem. You won't be able to make a connection even
if you try.
F While it is true that the cost of a 2400 bps modem is now at belowF $200, you should seriously consider the advantages a V.32bis modemC will give you. There is no question that the V.32 will give youF much more for your money especially if you can't find a 2400 modemG for less than $200. As V.32bis fax modems keep coming down in price9 the 9600 bps V.32 modems become even more affordable.
[1;33m Buyer Beware!
C It was once true that V.32 modems used to cost more than modemsC using proprietary modulation protocols. Hayes introduced theirB Smartmodem 9600, a V.32 modem, in 1988 with a $1999 price tag.E Current prices are now only about one-third on todays market. andD at present, New Zealand street prices for V.32 modems are to sayE the least not very reliable. Some prices being quoted just cannotD be justified. There are some retailers quoting a 9600 bps modemsC for a what others are quoting for 14,400 bps modems. So beware!
E Check out what it is your are buying. Don't just take for grantedD that the retailer is himself uptodate with current availability.B Beware of the retailer still flogging off old stock at the oldF inflated price. On the other hand - if the modem on offer does not9 have Telecom approval, why not? Again, buyer beware!
G Every modem manufacturer makes at least one V.32/V.42bis modem now,G and soon every manufacturer will also make a V.32bis/V.42bis modem.@ The price for V.32 and V.32bis modems will continue to drop.D Modems with proprietary modulation protocols are also being madeB with "dual standard" protocols that support V.32 and their ownD proprietary protocols. Packet-switching networks like Sprintnet= (Telenet) and CompuServe are also supporting V.32 modems.
B If I were in the market I would pay attention to this snippet.
[1;33m The importance of protocol
E To make the most of a high-speed modem, you need to know and haveE some understanding of three different kinds of protocols, and theA relationships among them. They are the modulation protocols,< error control protocols, and data compression protocols.
E A little technical for the average user, but not too difficult ifD you take time and don't panic. The way I understand it from theD information on hand is that the two modems (yours and the one atD the other end) can establish a connection only when they share aD common modulation protocol. To connect at high speed, two modems< have to support the same high-speed modulation protocol.
D Therefore, a modem with proprietary modulation protocol can onlyF establish a high-speed connection with another modem from the sameE manufacturer. eg. the U.S.Robotics HST modem can only establish aE high-speed connection (at 9600 or 14,400 bps) with another HST orF an USR Dual Standard modem. Or, as another example; a Courier HSTA modem cannot establish a high-speed connection with a CourierF V.32bis modem. They can only connect at 2400 bps. (All high-speedF modems in the market support the CCITT V.22bis modulation protocol% and will step down if necessary).
G This is why I prefer the alternative. Any two V.32 modems can talkD to each other at 9600 bps. They do not have to be from the sameF manufacturer. Any V.32bis modem can talk to another at 14,400 bps.B Any V.32 modem can talk to any V.32bis modem at 9600 bps. AndF another advantage is that besides high-speed modulation protocols,F all current models of high-speed modems also support error controlF and data compression protocols. Yes, you will have a higher priceE tag but you must ask yourself if the benefits are worth the extra cost.
[1;33m Error Control
E The two standards for error control protocols are MNP 4 and V.42.D The Microcom Networking Protocol, MNP, is developed by Microcom.E MNP 2 to 4 are error correction protocols common with 2400 modems/ and MNP-5 is the data compression protocol.
F V.42 is established by CCITT. V.42 actually incorporates two errorG control schemes. V.42 uses LAP-M (Link Access Procedure for Modems)E as the primary scheme and includes MNP-4 as the alternate scheme.E In this way a V.42 modem is able to establish an error-controlled5 connection with a modem that only supports MNP 4.
F A modem that uses a proprietary modulation protocol may also use aD non-standard error control protocol. For example, Hayes V-seriesD Smartmodem 9600 supports an error control protocol called LAP-B.F CompuCom's SpeedModem Champ also uses a non-standard error control
protocol.
C Modems like most 2400 bps Hayes-compatible modems, come without> error control protocols and cannot provide error-free data@ communications. The noise and other phone line anomalies areG beyond the capabilities of any standard modem to deliver error-freeC data. To help combat error-free communications the relationshipE between the modem and the software providing the protocol is very
important.
[1;33m Line Noise and Interference
D V.42 (and MNP 2-4) cope with phone line impairments by filteringG out the line noise and automatically retransmitting corrupted data.D If you have used a standard Hayes-compatible modem, you probablyF have noticed some garbled characters (like "@8d_w`[ce") show up on" your screen from time to time.
F When two modems establish an error-controlled connection, they areG said to have a reliable link and are capable of filtering out thoseF garbled characters caused by the line noise. Notice that the lineG noise is still there, but it does not show up on your screen or the screen on the remote system.
F The filtering process used by V.42 (and MNP 2-4) is similar to theD error correction scheme used by file transfer protocols (such asG Xmodem). The two modems use a sophisticated algorithm to make sureC that the data received match with the data sent. If there is a$ discrepancy, the data is resent.
[1;33m A Basic understanding of How it Works
G There are really three links involved in the process triggered when3 you invoke communications with a remote system.
E Besides the link between the two modems, there are still one linkE between your computer and your modem and another link between the) remote modem and the remote computer.
G When two modems attempt to make a reliable connection using V.42 orE MNP 4, only the data integrity between the two modems is ensured.F It is still possible for errors to occur at either end between theG serial port and the modem (in the cable) or in the computer itself.( (Fortunately, such errors are rare.)
D For extra protection use a file transfer protocol such as ZmodemG which also performs error checking even if you have a reliable link
with the remote system.
E There is a common misconception that Ymodem-g is much faster thanF other file transfer protocols. Although Ymodem-g is significantly5 faster than Ymodem, it offers little over Zmodem.
G Zmodem has proven to be extremely efficient. However, if Zmodem isF not supported by the system you are calling, use Ymodem-g. (If youD are connecting to a UNIX system in a university, you may have to, use Kermit or Xmodem to transfer files.)
[1;33m Setting Up Software To Work With High-speed Modems
E Getting a high-speed modem is only half the battle. You will need7 to get it to work with your communications program.
D Most communications programs still come with settings configuredC for standard 2400 bps modems. Since 2400 bps modems are Hayes-= compatible, it is relatively easy to set up the software.D You simply install the software as if you had a Hayes modem. TheB software usually will work flawlessly. And you do not have to6 worry about things like the initialization string.
B To get a high-speed modem to work with your software is a veryF different story. There is no longer a Hayes standard that everyone
follows.
F Here are some of the reasons why you need to know how to configureC your high-speed modem to work with your communications program.
G First, your high-speed modem may not be supported by your software.
E Second, even if your software supports your high-speed modem, the( software may not be set up properly.
[1;33m What needs to be checked ?
G 1. That the modem is initialized properly by the communications
software, and;
G 2. That the settings of your software match those of the modem.
G Finally, even if your software is set up properly, the settings mayG not work all the time. This may be because your modem may have beenF set up to operate on the factory default settings. While this mayG often produce the appearance of providing the best protocol, it mayD not in fact be so. Now you are about to get really involved withG the higher technology beyond the average Amiga user. Nevertheless,G be assured if your modem appears to be working without interferenceG or other problems appearing, then until you need to know what otherF bells and whistles can be unleashed - wait until you need to know.
[1;33m Things to come
[1;33mISDN
7 When will it be that we may not need modems at all.
E Integrated Services Digital Network (ISDN) has been around in forE some time now but has not yet become readily available. It still
costs an arm and a leg.
> When will ISDN really become available for the rest of us?
E It depends on your local telephone company. It is estimated thatF by the end of 1994 about half the telephone connections in the USAG will have access to it. With ISDN, you won't need a modem since noG modulation or demodulation will be necessary. You will need an ISDN
adapter instead.
A An ISDN line carries three digital channels: two "B" channelsF that carry various kinds of data at 64,000 bps and one "D" channelF to support 16,000 bps to carry control signals or serve as a third
data channel.
< A single ISDN channel able to transfer uncompressed dataG bidirectionally at 64,000 bps. Combine that with a data compressionH scheme and you will be able to transfer data at hundreds of kilobits
per second.
D Eventually, ISDN will provide widely available, low-cost digitalF communications for voice and data communication. But until ISDN isC firmly in place, high-speed modems will be with us for a while.
[1;33mV.fast
D CCITT is working on a new modem standard, dubbed V.fast. If allE goes well, the next modem standard is on the horizon. The V.fastD modem is expected to reach a raw speed of 19,200-24,000 bps over% standard dial-up telephone lines.
[1;33m Telepermit - the Telecom seal of approval
G The protocols, where referring to Bell and CCITT, are in most casesF compatable with Telecom in New Zealand. Although Telecom approvalE is required in New Zealand, modems currently marketed without theE Telecom approval are in the main reasonably compatable. However,F should you be operating any modem that is not approved by Telecom,B you could be in for some unexpected costs if your equipment isF found to be causing problems on the Telecom network. eg., problemsE generated by your modem going back through the phone line causing
interference.
E You may not realise it, but the agreement you signed with TelecomE for the phone connection you use (and presumably the one you willC be connecting your modem to) puts the onus on you. You have anF obligation to ensure that your modem carries a Telepermit when you8 connect it to the Telecom network (your phone line).
Q
[1mA word of caution:
[0m Telecom is empowered to disconnect equipment that? does not carry a Telepermit seal attached to the equipment.D Telecom can and will charge you for any visits it makes (to yourF place or any where else) while tracing any interference and chargeE you for the costs of any repairs to correct the interference. So,> before you buy, check that the modem carries a Telepermit.
B This article was reproduced specifically to assist Amiga UsersF throughout New Zealand with information touching some of the basicD questions most likely to be asked by users thinking of extendingF their Amiga experience by purchasing a modem and getting hooked on
a BBS.
G When preparing material about modems it is inevitable that you willD reach a point when the information leads to technical areas thatB may or may not be of interest to readers. For this reason theG material presented here does not go too far beyond the need to know1 for the basic introduction to Modems and BBS.
F For readers who may be interested in the more technical aspects ofF Modems and BBS, please give me a phone call, or write, enclosing a# stamped addressed envelope, to:
D If you send a disk with your stamped addressed envelope. I willF return it to you as a compilation disk "About Modems and BBS" fullF of useful hints and tips including information about communicationD packages and the cost of modems in New Zealand; who has the best
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