ADAPTOR OPENS UP THE MICRONET WORLD

Spectrum users can now take advantage of a growing database. Stephen Adams reports on the hardware which makes it possible.

The Prism VTX 5000 modem has been designed to give Spectrum users access to the Micronet 800 closed-user database on Prestel. It consists of a flat, black box slightly bigger than the Spectrum on which the Spectrum rests, connected to the modem via a three-plug ribbon cable. The cable connects the Spectrum and modem and provides an expansion connector for other peripherals like the printer. If you are using Interface 1, connect it to the interface connector.

On the front of the modem are two switches and two LEDs. The red LED is the power-on light and the green LED indicates to the user that the modem is connected via the line switch to the telephone line. The second switch allows you to select the mode to be used - Micronet terminal, half-duplex transmitting terminal with echo, or receiving terminal. The Micronet terminal works at 1,200 baud receive and 75 baud transmit to Prestel. The other terminals work at 1,200 baud both ways.

The connection to the telephone line is via a new-style jack plug and socket fitted by British Telecom. At present the cost of fitting it is being included in the price of the adaptor. The telephone is fitted with a plug on the end which plugs into the back of the modem or the wall socket.

The modem is approved by British Telecom but has no auto-dial facility, so the telephone must be used to dial the Prestel computer before the modem is switched-in. As long as the LINE switch is in the correct position it will not effect the use of the telephone and the unit can be left connected all the time.

The unit has two printed circuit boards, one to interface to the microcomputer and one containing the modem and isolation circuitry. The modem is a Texas one-chip modem type TCX3101 controlled by a 4.4MHz PAL colour frequency crystal. It has amplifiers between it and the line and provides various handshaking signals to the communications interface chip via a 10-wire interface cable. The board also contains an isolation transformer and a reed relay to hold a telephone call when the handset is replaced on the telephone.

The Spectrum interface board contains an 8251 communications chip, 8K EPROM, baud rate oscillator and various decoding chips which allow it to switch-out the 16K Sinclair Basic ROM and replace it with its own.

Various speeds are available, the RS232-type interface being marked from 75 to 2,400 baud, but the board is connected to work only at 1,200 or 75 baud. The chip is operated by a 0 on bit 7 of an I/O address but checks the lower five hits to see if a Sinclair device is requested. That may affect some other devices like joysticks, which also use that method of addressing.

On powering-up the modem and Spectrum - the modem is powered from the Spectrum via a voltage regulator by turning it on at the mains plug - the modem switches in the 8K EPROM and loads a Basic and machine code program from the ROM into RAM. It also loads a new Prestel graphics set above RAM TOP. A warning is printed in the front of the manual about not powering-up by plugging-in the power socket to the back of the Spectrum when using Interface 1 - the Microdrive interface. Do not ignore it as some damage may occur if you do.

The Basic program then RUNs and presents the user with the Micronet 800 logo, which also gives the software version number and date. Pressing a key will then get you on to the main menu, one of five used to control the system.

That gives seven functions and is returned to for SAVEing and LOADing software from Prestel, saving, printing or viewing frames - each page is called a frame - entering other menus or entering or leaving Prestel.

Option one lets you log-on to Prestel after inserting your identity number and password into the computer. That may be done before or after obtaining Prestel. The number is issued by Prestel via Micronet and is the one by which you are charged, so do not let anyone else have the number or they could incur large bills which you would have to pay.

To contact Prestel dial the number for the local Prestel computer - it will always be a local number to save cost to the user - and wait for the computer to answer with a high-pitched tone. Then throw the line switch on the modem and replace the handset on the telephone; that prevents noise from the telephone corrupting the data.

The control of the telephone line is then with the Spectrum. You are then ready to use Micronet 800, from whose page you start, or other open Prestel facilities. Micronet and other closed databases are restricted to members who pay a subscription to join. In the case of Micronet it is £52 per year.

Micronet 800 provides facilities for exchanging messages with other users, including the Information Providers; ordering goods; downloading free programs; or buying programs which are downloaded to you over the telephone. There are also various news and information pages on BBC and Spectrum machines.

The present database of free programs seems to be made up of programs seen in Sinclair User and the amount of programs for sale is limited. There are two 16K programs and about 10 48K programs and none of the famous names is among them either.

None of the major software houses for Spectrum software seem to want to use Prestel to sell their programs but that may change as more users log-on from Spectrums.

The Prestel page is 40 columns by 24 lines and so the character set has been altered to give the smaller characters required, as well as re-defining the graphics characters. Various features also allow you to specify colours and use FLASH or REVEAL functions.

The page number is always printed at the top with the price of the page and what kind of page it is - in this case Micronet 800. At the bottom of the page is anything you type-in at the keyboard.

Only numbers, the two SHIFT keys, and ENTER are recognised. To get out of any frame press CAPS SHIFT and ENTER, which will return you to the main menu, from which you can get back to Basic by pressing 7.

Any of the frames can be copied to the Sinclair printer, stored in RAM or on tape. The screens are stored as a single DIMensioned variable B$(600) and are SAVEd and LOADed as DATA. The terminal software uses normal 32-character Spectrum screens for the menus.

The frames for programs have the first two pages as an introduction and from page number c onwards they consist of the data stored in CET format at about 850 bytes per frame. Micronet always starts loading from page c until the last page unless it is told by the user from the downloading menu.

When LOGging OFF Prestel, a response page is printed if there are any messages in the mailbox for you. You then have a choice of reading them, erasing them or storing them on tape like any other page.

Using Prestel can become very boring, as the only facilities you have are the numbers 0-9, the SYMBOL SHIFT key - used as * - and the ENTER key - used as #. To work your way through to a particular page you can either go direct to the page, if you know it, by * Page number #, or by using one key to select from a menu the next descending menu, until you reach the page you want.

All the time you are doing that you will be charged for the price of a local telephone call. If you intend to use Prestel a good deal it is worth storing some of the index pages on tape via the Save Frame facility, as they can allow you to pick up the correct page immediately.

As the control program is written in Basic it would not be too difficult to alter it to do a search of Prestel for the information you want, or to call a certain page automatically.

That would certainly speed the access to the information and save money on telephone bills. That kind of program would have to be SAVEd on tape, as the original program would be installed on switch-on.

You do not have to be connected to Prestel to view pages stored on tape and the terminal software allows you to leave Prestel and do something on the computer and then return to it where you left off. That will happen also when you download software as it over-writes the Basic program.

To return to Prestel you type RAND USER and then a number, which depends on whether you own a 16K or 48K Spectrum. The only way to leave Prestel is to LOG OFF on the main menu or by changing the LINE switch. For this a computer can be connected between 8am and 6pm from Monday to Friday and between 8am and 1pm on Saturday. An additional fivepence a minute will be added to the normal local telephone charge. More details can be found on page 123 on Prestel or by telephoning Freephone 2043.

The instructions with the package are simple and easy to understand, with plenty of pages reproduced by a Sinclair printer. The only facility not mentioned is the two terminal facilities, TX and RX. TX allows you to send data and programs at 1,200 baud to another user using a 1,200 baud modem. Any data sent is also echoed to the Spectrum for printing on the screen, which is a useful way of checking it is working. You can transmit only in this mode and cannot see anything sent to you.

The RX mode is the same as the TX mode, except that any characters typed in are not echoed, but are lost. So to talk to another user you must move the switch constantly from TX to RX and back again. There is a software switch for it but at the moment there is no software to run it.

Micronet 800 and the Prism VTX 5000 modem allow you access to the database, at a price. The cost of the modem is £74.95 plus £13.15 per quar ter plus VAT.

For that you get access to Prestel and Micronet 800; a free jack socket is fitted within 72 hours by British Telecom where your telephone was sited. Also the telephone has a new cord to allow it to plug into the socket.

Those charges are made quarterly, so it would be better to keep a note of how much time you spend and when, as you go along, so you do not receive a massive bill.

The usefulness of having all this information on tap 24 hours a day, seven days a week, will depend on how much it costs to get it and what is available. On Micronet the information side is just getting started for the Spectrum and the cost is high.

Prestel has more information in it, as it has been operating longer, and information on airlines, railways, pubs, clubs, theatres in any area of the country could be very useful if you want to make a reservation.

The more people who use the system, of course, the better the system becomes and possibly the cheaper it becomes.

The VTX modem provides the key to the door and I had no problems using it which were attributable to the modem. It is for users of the system to explore this new world like an adventure game, publishing the interesting pieces - and the annoying ones - for everyone else to see.

Using the mailbox facility, messages could arrive by Micronet and not by post in the near future, taking seconds instead of days. It could also solve the commuting problem by you doing your work from home via a Prestel terminal.

Micronet 800 is at Scriptor Court, 155 Farringdon Road, London EC1R 3AD. Tel: 01-278 3143.

Jack Russell reviews adaptors for the Spectrum, BBC and ZX-81 Micros.

This review covers several packages available for the popular BBC Micro and ZX Spectrum computers which allow them to operate as viewdata terminals. This means that services such as Prestel can be accessed without having to buy a special terminal.

The VTX 500 ZX Spectrum adaptor consists of a flat black plastic box containing the modem which fits under the computer. There is a ribbon cable and connector which plugs into the back of the Spectrum and further devices such as a printer can be connected on to a spare connector on the ribbon cable. There is a telephone type cable out of the VTX 5000 which will plug into a standard British Telecom wall socket.

Your telephone then plugs back into a socket on the back of the adaptor, allowing yon to use the phone normally. The BBC system supplied had a slightly larger box which attached to the computer via a cable into the RS-423 connector. This box could then be placed under the telephone. In addition the BBC adaptor had an EPROM chip which had to be fitted into one of the spare "sideways" ROM sockets in the computer.

When the Spectrum is switched on a start up screen appears inviting you to press any key. When this is done the Main Menu is displayed. To get to this stage on the BBC Micro the command.

*MIC.

needs to be typed. It is from this menu that all the features of the package can be controlled. Items on the menu include: log on, terminal operation, save/view frames, print frames, download and mailbox editor.

To use Prestel it is necessary to log on to the system. When the menu option to do this is selected the program prompts for your ID number. This is then sent to Prestel when a connection is established. Upon dialling up the Prestel phone number and flipping the switch on the modem to on-line the screen is cleared and the Prestel sign-on frame appears.

All normal Prestel facilities can then be used. Frames can be read just by pressing the number keys and the special keys* and £. To return to the menu the keys Caps Shift and Enter on the Spectrum or Tab on the BBC are used. This allows the use of other functions in the package such as saving frames on tape or disc, printing and so on.

Everything appeared to work correctly so next I tried downloading a 'free' telesoftware program. The downloading operation seemed to work well but I was not too impressed with the quality of the 'free' programs on offer. On the Spectrum it is necessary to restart the terminal program after downloading because the support program gets overwritten by the downloaded one. When this restart function is performed the main menu is displayed again and selecting the Terminal option takes you back to Prestel.

The final function provided was an editor to prepare mailbox frames while offline. I was not impressed by this part of the package as only one line at a time can be edited and it is not possible to correct errors in earlier lines; the whole message must be retyped from the start. I'm sure that improvements could be made here. However, I think that the Mailbox facility is one of the most exciting things about Prestel.

The modem hardware worked well and I had no trouble downloading some software. The Spectrum package in particular was impressive in being able to produce a 40 column full colour Prestel display.

ON LINE

Ray Elder describes his close encounter with British Telecom.

This is an account of how I became one of Prestel's customers, and a description of what the computer information service offers from the point of an interested incompetent.

I have always been fascinated by the more practical aspects of computing, you only have to remember my previous project on using a Spectrum for word processing to realise that, and the thought of being able to access the information on British Telecom's computer intrigued me.

Early in June I contacted Micronet 800, a computer specialist user group who provide an information service on the Prestel Database, and applied for registration with them.

Prestel is very similar to Ceefax and Teletext, services offered by the TV companies, in display and basic functions but with two very important differences.

The first is that you can communicate with Prestel by sending messages, replies to questions and quizzes and also download information and programs into your computer or to a printer for a permanent copy.

The second is that you have to pay for it! however at off peak times, after 6.00pm weekdays or 12.00 Saturday or all day Sunday the use of the computer is free, but you still have to pay the standard phone charges either at local or national rates depending on which computer you contact.

In order to use the Prestel computer you must be a member of one of it's user groups, once you become a member then you have access to all the other information in the database except for some pages which another user group has set up and may want to keep private.

Having phoned Micronet, (01-278 3143), a few days later a letter and an application form arrived. I dutifully completed said form and returned it to them the same day. I was starting to become quite excited about it.

THE EQUIPMENT

Before I continue the saga any further it is worth mentioning the various boxes which will allow you to connect your computer to BT's lines. Note that any equipment attached to the phone needs to be approved by BT, so look for their approval sticker before purchasing anything, A specialist system of a keyboard/keypad and a connection device can be acquired, but for one purposes I'll take a brief look at the modems available to link up the Sinclair computers, both Spectrum and ZX81.

By the way, the modem is a MOdulator/DEModulator and is the device which connects the computer to the phone lines and by which the signals to and from the computer are matched to the signal that is sent over the phone lines.

This use of a universal standard means that you can communicate with someone who is using a completely different micro and not only another Sinclair user.

There are two methods of making the connection, probably the cheapest is by an acoustic coupler. This is a rubber device into which you insert the telephone handset and all signals are sent audibly. The computer is then loaded up with accompanying software and the connection is made as normal.

The disadvantage with this system is that in a noisy environment extraneous noise may cause the link to fail. An advantage is that if you own a portable computer then information can be sent from a call box anywhere in the world and collected later on your home (or office) based machine.

The other method is by using a direct connection via the detachable telephone socket that is fitted to the latest phones installed. If you have the old type of connection then BT will have to change it, this may cost £25.00, but many "special" offers are around and Micronet were (and may still be) providing this free when I joined.

MEANWHILE...

A week after I posted my application a large envelope bounced off the doormat and was quickly sat on by the cat. After removing the moggie I tore it open (the envelope, not the cat) and found a nicely produced folder of information, a Prestel contributors directory, a welcome letter and an advertising brochure from a well known credit card organisation.

The people who provide and maintain the pages are known as Information Providers or IP's - yet another bit of jargon to remember.

The letter proclaimed "WELCOME TO MICRONET 800! YOU ARE NOW ONLINE TO ONE OF THE WORLD'S LARGEST DATABASES." Except I wasn't.

My phone had one of the older type of connectors and I couldn't link up to the phone lines until a BT chappie changed it. I also had another problem. My phone was situated in the small entrance hall at the front of the house, my computer was set up at the back.

There was no room to put the machine with the phone and it wasn't practical to have a 20ft lead running through the centre of the living room, not with a cat that attacks anything, a child who eats anything and other members of the family including myself, who'll trip over anything.

So the phone would have to be moved. No great problem as the line arrived at the back of the house anyway, all they'd need to do was drop it down, bring it in the window and add the new connector.

The other reason that I wasn't online was that all users have their own customer identity and password to prevent someone else from using the service at your expense, this would be forwarded in a separate envelope later.

With all this justified security I was expecting Securicor and full escort to arrive and not just the plain brown envelope that eventually was sat on by the cat.

Excitement becoming more intense.

THE SPECTRUM BOX

The unit which I am using is the Prism VTX5000, this is a direct connection device which fits under the Spectrum and is the same length but slightly deeper so that a bit will either stick out in front or at the back. It is compact and has an ON light, a LINE light connected to a toggle switch and a 3 way slide switch marked M/NET, Tx and Rx on the front.

A lead comes from the back of the unit and is plugged into the phone socket, the telephone lead is then plugged into the socket provided at the back of the modem.

A connector ribbon is supplied which has three sockets, one for the back of the unit, one to fit the Spectrum's port and one which provides an extension for the printer etc. This lead was rather short and I would have liked it to have been longer to allow for non standard set ups.

I do not have a Microdrive as yet, but I can foresee difficulties in using both together, some unsatisfactory lashing together of leads and the devices would have to be undertaken. I have my Spectrum housed in a DK'Tronics keyboard and there was no chance of the modem fitting beneath it!

I solved the problem by putting the modem on top of the keyboard and plugging one socket into a Currah micro slot adapter. The unit hangs over the back and I support it with wooden block legs, this is only satisfactory because the whole lot is permanently housed in a cabinet and the back is not seen.

The manual is a work of art, only a genius could make something so simple so confusing!

Actually each section of the manual is written in a very clear step by step manner, its just that the sections were put together in a confusing way. The main sections dealing with operating the modem are in two chapters, "The main features" and "User instructions in more detail".

Being a 'do it by numbers' type idiot, I found myself trying to operate the system from the first section which does not contain an adequate explanation. It would have been better if all the details of "How to log on" for instance, were not split into the two sections.

On Wednesday the BT engineer called, I was out, my wife explained what was required, move phone from front to back of house.

"Ummm. Very sorry, that's an 'outside' engineers job. Can't do it, I'll talk to the boss" and away he went. The next week two of them turned up and spent a day drinking tea and climbing ladders. Eventually the phone was repositioned, a very neat job, they even fitted two sockets and also managed to sell us a new phone!

Cost £18.00 (the reason I'm quoting prices is so the Taxman will make an allowance).

Fine - except that the phone now permanently picks up Radio 4 and this does not seem to be appreciated by Prestel. Excitement reached fever pitch.

ZX81 BOX

I'm afraid that I haven't been able to test out the ZX81 adaptor as either my letter to them has been lost in the post, or the unit has been delayed on its trip to us. I will quote from the information I have.

The unit fits between the ZX81 and the RAM pack and other peripherals such as the printer, and it can be used in conjunction with both acoustic and directly connected modems. With both ZX81 and Spectrum units the screen is changed into a 40 character per line format and the double height and graphic modes are also used.

The ZX81 loses the colour, flash and more sophisticated screen controls but the Spectrum unit copes admirably.

I have been told that the ZX81 screen does not completely fit onto the TV and that a sideways scroll is provided to allow you to read all the text.

Considering the problems it sounds like an ingenious device!

THE LAST ROUNDUP

Finally all was ready, connected and powered up. Here we go! As soon as the Spectrum was switched on the Micronet 800 logo appeared, on pressing a key a menu of seven options was presented, the last being to go to BASIC.

I am using the ZX LPrint III Centronics interface to drive a Shinwa printer, this has to be initialised before use so I pressed seven. The machine then reset, ie cleared out all programs and gave the usual Sinclair copywrite notice.

I initialised the interface and then stopped. There was no way of getting back to the Modem program bar turning off and on the power to the machine, and this would mean the interface would need to be reinitialised!

After many attempts I discovered that by getting into LOAD or SAVE mode from the modem and pressing BREAK, I could initialise the interface and get back to the modem. Fortunately they had allowed for load/save problems and also you may need to get back after downloading software.

Right, option 0, enter my identity, phone number given. When carrier tone (a high pitched whistle) is heard switch on modem, replace phone.

I did. It worked!

After entering my personal password I was greeted by name and allowed free access to the whole lot, and what a lot there is. I haven't counted but there are hundreds, probably thousands of different companies providing information. I was able to demonstrate its use to four people, none of them interested in computers, by finding a subject they were interested in, wines, photography, camping and money.

I was able to save screens on tape or printer for a permanent copy, download software, some free - perhaps not professional quality, but what can you expect - and some charged for.

I can order goods through this system by quoting my credit card number (now I understand why American Express sent their brochure) or reply to questionaires.

I can send and receive messages to other users on the Micronet mailbox, and by joining Directel, another user group, I can use their mailbox facilities.

I also found a "personal" section somewhere in the system which was very amusing, a set of messages to and from users almost like an electronic version of CB.

It would take months to just look at all the info, held in the system, but I'm convinced there must be something for everybody and personally I find it the most exciting development that I've encountered.

A word of warning, it is easy to become so engrossed in the system that you lose track of time, remember that all the time you are on line you are being charged for your call at the appropriate rate!

So far I must have spent enough time logged on to keep Buzby in birdseed for a year or two!

I adorn this article with some samples of the Prestel IP pages, and if any readers are using Micronet already or link up in the figure, then I can be contacted through Mailbox and my number is 919993265, whether I will be able to manage to find the time to reply to everyone who writes will depend on how many people make contact. As usual I'll do my best.

MODEM ROUTE TO SUCCESS

A good modem can cost as much as a computer. Anthony Thompson investigates.

Price: £70
Baud Rate: B
Auto Dial As Standard: No

Every branch of computing has its own set of jargon. With word-processors you can cut, paste, insert or zap. With joysticks you can have auto-fire, pistol grips and microswitches and with monitors you can have RGBs, dual frequency and monochrome display. In most cases, common sense will give you a rough idea of what the jargon means but there is one area of computing where you might need a little help.

Communications is an area filled with seemingly meaningless phrases but one which offers rich rewards to those who dare to enter; to link your computer to the world of unlimited telephone bills, all you need is a modem.

The word modem is an abbreviation of modulator-demodulator. It is a device which translates the electronic language of a computer into a series of sound waves and vice versa. Those sounds are then sent down a telephone line to whatever service you choose.

All modems require software to work. With some models such as the Miracle Technology 64 multimodem it is built-in, while others like the Datastar Magic modem require a separate package. Software varies in price depending on the machine and the number of features you want.

AUTO-DIALLING

More expensive systems may incorporate more facilities such as auto-dialling and answering, on-screen clocks and memory buffers to store incoming data. Such features are really worth buying only if you intend to make full use of them. An auto-answer machine, combined with the correct software package, will allow you to create your own bulletin board with whatever services you like, but unless you do not use your telephone a great deal, it is best to have a separate line installed.

Modems in the same price range tend to have similar functions. The more expensive models have several additional features but the value is dependent on the purpose for which you intend to use it most.

The baud rate, the speed at which the modem sends and receives data, is an important consideration. Some systems send and receive data at 300/300 baud, the equivalent of 30 characters per second, but more recently many viewdata and bulletin board systems have adopted the Prestel standard of 1,200/75. While more and more systems are using that speed, the number still using 300/300 is sufficient to justify buying a modem which can handle both.

Faster speeds are available but they cost considerably more and can really be used only with the commercial electronic mail systems; they are geared more towards business than home users.

Most modern modems connect directly into the telephone socket. For those whose homes use older-type connections, acoustically-coupled modems which incorporate rubber cups to fit on the handset are available but they are often more difficult to use.

Modems capable of faster speeds such as 1,200/1,200 are available but they cost considerably more and can really be used only with commercial electronic mail systems which are geared more towards business rather than home users.

The operating speed of a modem is sometimes defined by the V system. That relates to a set of recommendations for data transmission by telephone made by the United Nations technical committee. V21 refers to the 300/300 system while V23 includes 1,200/75. There is also V22, the 1,200/1,200 system, and others which define modems which can auto-dial, auto-answer and so on.

Modems are sometimes also defined as being intelligent or Hayes-compatible; the latter refers to an American standard and the AT command set which some software packages use. Using this system, to dial a number from the keyboard, you type ATD followed by the number and return. The AT command attracts the attention of the modem while the D tells the modem to dial. Variations of the command set include help functions and dialling from memory.

Most modern modems connect directly into a telephone socket. For those whose homes use older-type connections, acoustically-coupled modems which incorporate rubber cups to fit on the handset are available but they are often more difficult to use.

A final point to mention is to ensure that the modem you buy is BABT-approved. If it is, it will display the green approval sticker - it is a criminal offence to use a non-approved modem on the BT network.

BITS 'N' PIECES

My, how it's grown - almost a MegaSpectrum! Which of these useful little add-ons could you do with on your Speccy? To help you choose, Stephen Adams has done his bit and come up with a piecemeal review of them all.

8. VTX 5000
Modem House
£49.95

With one of these modems you'll have all the equipment you need to operate a telephone line through your Spectrum - though you'll still have to do the dialling manually! Prestel software is supplied in ROM and if you're quick on the uptake you can get three month's Micronet subscription free. You can also use your modem to swop program data or code with your friends and/or different computers via a Bulletin Board - one of the free message systems dotted around the country. If you're in business, you can also use it to send telexes (through Prestel or Telecom Gold) as well as having an electronic mailbox for letters that take only a few seconds to post. These applications require special software but that can be picked up quite cheaply from Modem House. A word of warning, though - watch your phone bill as using a modem can become habit-forming!

WIRED

YS presents a handy-dandy guide to having fun with your peripherals. And who better to lead us down the hardware path than JON PILLAR? Quite a lot of people to be honest, but they were all at lunch.

There's more to life than playing Speccy games. Using Speccy hardware is also to be recommended. Over the years a huge number of little black boxes have appeared for plugging into the back of everyone's favourite, um, little black box. Sadly, a lot of these have now gone forever. The Specdrum, the Slomo, the Music Machine... where are they now? Actually, they're still around, you just have to look rather hard for 'em. For those of you who can't be bothered looking rather hard, there are still plenty of goodies to be collected.

VTX5000 MODEM
BG Services/£15

The wonderful world of communications, eh? How else could you swell BT's bloated coffers by chatting about the weather with Ned Gimp from Hawaii? The VTX5000 links you up, via an ordinary household phone socket, to bulletin boards and network services across the country. (Or, indeed, the globe.) The actual VTX itself is a pretty ancient machine - if modems were tins of wallpaper paste, the VTX would be a very old tin of wallpaper paste. It's a 1200/75 device, receiving data at 1200 baud, and transmitting it at 75 baud.

What's a baud? I'm glad you asked me that question. It's the unit of time taken to move one bit of data through a phone line. I think. 75 baud is the slowest rate possible, which goes to show just how old the VTX is. Thankfully, due to the widespread use of the modem, plenty of PD terminal emulators and other bits of driver software have sprung up - some of them extremely sophisticated, which makes life that ever so vital bit easier. In fact, the only problem I had with BG's modem package was that it assumes a certain amount of techy knowledge on the user's part. As the nearest I've previously been to a modem is Putney, it was a bit of a struggle to get things started. Logging onto the various boards themselves is fairly painless, although if you live outside the London/Reading area you'd better be prepared for some stonking phone bills. Once you've connected to a service, you can while away the hours swapping gossip, downloading software and promising your mum that you really will be in bed by 3am. Alternatively, if you can coax a pal into buying another VTX, you can use BG's User to User program, which allows you to chatter away electronically between yourselves to your heart's content. Overall, a fun bit of kit, though half the fun is figuring out which boards you can connect to!

IT'S ALL GOING HORRIBLY WRONG DEPARTMENT

Speccies are like mushrooms. If you keep them warm and nurtured, they flourish. But if you trample them into the ground or allow your dog to eat them while walking in the woods, they tend to fall over. Furthermore, I wouldn't recommend that you put them in a pan and cook them with a nice free-range egg in an attempt to make a mushroom omelette, because it won't work. Um, actually, Speccies aren't like mushrooms at all. Forget I said that bit.

Anyway. The point I'm failing quite spectacularly to make is that Speccies are temperamental beasties. Inevitably, they'll break down. And while the most sensible course of action is to take your ill machine along to an authorised repair centre, you can fix some things in the comfort of your own home. But be sure to have a responsible adult on hand. They will then say, "I told you that you should have gone to an authorised repair centre," in a patronising tone of voice when you bodge the job and wreck your Spec. If you feel up to the task though, quite a few companies offer Speccy spares - everything from new ROM chips to new +3 disk drives. WAVE are particularly well-endowed with small bits of Speccies. Their catalogue has just about everything you need to build your own machine! Buy the spares direct, put them aside for that fateful day, and it'll be cheaper to repair your Speccy yourself. Or else get your local soldering iron whizz to do it for you. Just don't say we didn't warn you if things go even more horribly wrong.

Well, that's it. Hopefully this little trip through hardware land has been useful and informative. If not, why should I care? I'm off to digitise the climax of The Terminator and save it out to disk as an animated sequence. Just don't tell anyone, or they'll all be at it…

MORE MODEM MANIA

In the last issue of Tech Niche we promised you a review of Spectrum modems. On the face of it that was a little bold, not only because there are so many modems about but also because the manufacturers of them are either a) mean b) hard to find c) don't want to be found or d) they never really had a modem in the first place.

Anyway enough excuses. We did manage to decide on the two most important modems to review in this issue and we'll pass over the other for the meantime.

The VTX 5000 and the Protek 1200 modems are both front runners simply because they provide an uncomplicated means of communicating with Prestel or, perhaps more importantly Micronet, at a reasonable cost. These two modems are limited because they do not provide the facilities that would allow you to communicate easily with every sort of on line computer there is - there are modems that do, but generally they cost a lot more and are more complicated to set up. When we reach the stage of examining hobbyist bulletin boards and specialist databases we shall also examine some of the kit that is needed to make those connections. But they will have to wait for a future Niche.

To begin to explain why modern compatibility is nearly as big a laugh as computer software compatibility, it is necessary to take a look at the workings of modems. As stated in the last issue Modem is simply a shortened form of MOdulator DEModulator. We all know that computers hump information around internally as representations of one's and zero's. Computers really aren't that smart: to a computer life is very simple, a situation is either black or white, on or off, one or zero. All this means is that if a computer wants to tell somebody that it knows The Answer it can't simply shout out 'forty two', well it can, but only because the computer knows how to turn its version of 'forty two', 101010, into our version of 'forty two' - 42.

So if one computer wants to chat to another computer it will do so in a signal representing binary numbers, and all that the modem does is to take the binary message and turn it into a form that can be sent down a standard telephone line. Fed with data in serial rather than parallel form, all a modem does is convert characters into sequences of notes for transmission, and decode incoming signals which have been sent down the telephone line, assemble them into characters and hand them over to its host computer.

In the case of the basic Spectrum, which doesn't have a RS232 port fitted as standard, you either need to get hold of a modem which connects directly to the edge connector and sorts out the interfacing problem for itself, or use a suitable RS232 interface for your Spectrum which should allow you to connect it to any modem. The RS232 interface provided on Interface 1 isn't up to the job, although people are rumoured to working on that problem.

Once you've got a modem attached to a Spectrum and working, the next problem is to make sure that it is compatible with the modem at the other end of the the line. They must both talk the same language in order to hold a successful conversation. A number of variables are involved, the two most important of which concern the speed with which the signal is sent and the pitch of the notes used.

In Europe we have two main standards. CCITT V.21 which is for 300/300 baud communications, and the V.23 for 1200/75. The baud rate is a measure of the speed at which data is transmitted. Typically, 300 baud represents a rate of about 30 characters a second, while 1200 baud is about the fastest speed of transmission achievable on a normal telephone line, and works out at about three lines of text on the Spectrum screen per second.

The V.21 standard is used by most hobbyist bulletin boards and on-line services. If you want a modem to talk to these chaps then it must be able to adopt that standard (neither the VTX or the Protek can). The most widely used standard now being used by Spectrum owners, due largely to Micronet, is the 1200/75 baud V.23. This is the standard adopted by Prestel which sends frames at 1200 baud and receives instructions at 75 baud. It was this standard that the VTX and Protek modems were designed to use. Some bulletin boards cater for 1200/75 communications, however, and user-to-user communication is also possible with these modems.

If you have a burning desire to go truly international and communicate with systems in the USA or Canada, then you will have to consider yet another range of standards. The American Bell 103 is similar to our V.21 and the Bell 202 is like our Prestel (V.23) standard except that Bell uses different pitches to CCITT systems. Modems are around that can switch between all these different standards - but at a price. We hope to bring you news of one of these, the new Miracle Modems Spectrum version soon. There's no point on lashing out on super whizzo (and expensive) hardware if your main interest is in talking to Prestel and Micronet, however.

Apart from the communications software needed to drive the modem itself and sort out such housekeeping problems as word length and parity so that the receiving modem on a system is sent what it expects to receive, a further problem can arise from lack of compatibility with software. Clearly the computer that you want to talk to and your computer both need software to organise a multitude of functions be it simply transmitting chunks of text to another computer or sending a message to a mailbox on a large system.

The problem is that each computer has a different view of the outside world. For example, problems may be caused by incompatible character sets. Prestel would never understand what a Spectrum SYMBOL SHIFT keypress was meant to mean, but software converts it to be sent as a star - that's fine because the Prestel machine knows that the star means an instruction is on it's way. Saves a lot of argument and down time with grumpy computers does the software.

Remember that no matter how smart a modem is, without the software it's just a pile of chips and capacitors. The software that comes with the VTX and the Protek modems is able to convert the Spectrum's output into a form understood by Prestel, and a few more clever tasks besides.

THE PRISM VTX 5000
Supplier: Modem House
Price: £49.95

This modem really seems to have become the standard for clever people (a recent survey shows that most clever people own Spectrums Source: SEOS 1985). The principal advantages with the VTX are two fold. Firstly the software is held on ROM (read only memory) which means the machine is raring to go on power up so time is saved especially when, as often happens, your connection with the mainframe is broken and you have to reset the Speccy. The second advantage is that the modem is hard wired, plugging into the phone socket and then the phone plugs into the back of the modem. This greatly reduces the chances of the modem being interfered with by outside noises! The software has most of the functions that you could need including automatic log on and off. Micronet frames can be saved to tape or microdrive and printed out, you are able to download the software or compile messages off line loaded to tape ready to be sent when you are on line. The VTX can be used as a user to user modem to allow you to communicate with other users so long as the same V.23 standard is observed. Other software is available for the machine which allows you contact databases and bulletin boards that use the same speeds but transmit text in an rolling form as opposed to screen by screen. Specnet by Stephen Adams costs £5.95 and a similar package by Stephen Gold can be downloaded from Micronet for a small charge.

CONCLUSION

In my opinion the extra £10 for the VTX modem is more than justified. It is easier to use and simple to set up, it is moderately idiot proof as well as being neat and tidy when in operation. The only advantage that the Protek may have is that the acoustic coupler could, in theory, be used with any computer that can supply it with RS232 input providing you can write, buy or scrounge the appropriate software to drive it.