COMMUNICATING DOWN THE LINE

The Protek 1200 modem and Spectrum interface are now available and can operate in two modes, 1200/75 for database connection such as Prestel and Micronet 800 and 1200/1200 for user-to-user communication over the telephone lines.

In Prestel mode the Spectrum becomes a Prestel keypad and basic information on using it in that mode is given in the instructions.

In user-to-user mode the other party you are contacting must also have a Protek 1200 modem running under the same software. After setting up the telephone link, informing the system of where the file you want to send sits in memory and defining block start and size for the code you are ready to transfer data.

Priced at £59.95 for the modem and £24.95 for the Spectrum interface they are available from Protek Computing.

MODEMS AGAIN

The much talked about modem from Protek has finally been launched. It's an acoustic coupler which means that, instead of wiring it directly to your phone, you just plug the handset into the two rubber cups on the modem itself. This works fine for standard phones but won't fit if you have one of those posh trimphones.

The modem works at 1200/1200 baud half duplex and 1200/75 baud full duplex and is fully BT approved. The first standard is used for talking to other Protek modems and sending listings and data to your friends through the phone network. The 1200/75 option will allow you to link into Micronet and Prestel.

The cost is just £60, which really is good value. Before you can use it, though, you'll need some software, a cable and, for some micros, a special interface. This costs £14.95 or £24.95, depending on whether or not you need the RS232 interface.

The software which drives the modem is, to say the least, not very good. The BBC version is the best and will certainly let you into Micronet and Prestel. But because pressing the ESCape key will put you back to the program's menu, you can't actually end an ESCape character to Prestel. This rules out colour-coded Mailboxes and pretty frame designs.

The Commodore 64 version suffers from the same problems and also lacks a return key as this is used for a Prestel hash character (#). This means that, at the moment, you can't use the system for connecting to Telecom Gold, despite Protek's claims to the contrary.

The Spectrum version is awful. Instead of displaying the Prestel screen as it comes down the phone line character by character, it waits for the whole frame and then displays it at the end. So when you call up a page, you have to wait quite a few seconds before it appears, just like teletext and rather disappointing.

If only the software was as good as the modem. But that's what you have to do to keep down your costs. Apparently, it would have added around £10 to the Spectrum version's cost to provide a proper display. I'd have paid - wouldn't you?

Protek are in Scotland on 0506 415353.

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 PROTEK 1200
Supplier: Protek and high street shops
Price: £39.95

The battery powered Protek machine is £10 cheaper than the VTX, but it presents the disadvantages of having to load the software into your machine before you can go on line. Also, the modem is acoustically coupled, which can give you some very undignified moments as you try to squidge your handset into the two rubber cups. If you have a trimfone or a phone in a style other than the traditional one then forget it, but being battery powered the modem has certain portability advantages (only really advantageous when you get your Spectrum running off batteries too, though!) While the software is as useful as that of the VTX it is not as easy to use since some functions require you to load in the odd chunk. If you want to use the modem user to user you have to agree which one of you is to be the original sender and who is to receive and then load in the appropriate code. With the VTX modem you only have to slide a switch.

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.