|★ HARDWARE ★ PERIPHERIQUES ★ INTERFACE : Teletext Adaptor and Tuner for AMSTRAD CPC ★|
|Interfaces Microtext|Amstrad Computer User)||Hardware Peripheriques|
IT has now been more than a year since my teletext TV gave its final performance. Since then I've often felt to be out of things, not being able to read up-to-the-minute news and sports reports at will. I was therefore delighted to get hold of a Microtext Teletext Adaptor and get stuck into all the things I'd missed.
Once again I could keep tabs on obscure golf tournaments and page the football league tables in blissful optimism that my team was leading the pack.
Once again I could consult the business pages to gloat over the bad performances of the shares I had chosen not to buy, trying to convince myself that I can't be wrong all the time.
The adaptor responsible for my feelings of failure is the only product that Microtext produces. It is attractively housed in a sturdy, black plastic box and plugs into the expansion port of a 664/6128, or the disc drive port on a 464. Its through connector allows for the addition of
Supplied with the unit is a lead to connect it to a video recorder, software on tape, and an easy-to-follow instruction book. Provided a video recorder is available, this is all that is needed to put the four BBC and ITV teletext channels on your monitor screen. Without a video recorder, the additional tuner unit is necessary.
The point I need to make here is that teletext signals are transmitted with each TV channel. The only way to decode and use them is via TV tuners and all video recorders have their own built-in tuners to allow the recording of one channel while watching another.
Microtext has cleverly designed its unit in two parts, allowing video owners to make use of their recorder's tuners, thereby keeping the cost down.
For those who don't own a video, or who prefer their computer and video to be separate, the tuner unit - which looks very much like the teletext unit - is available with connecting lead and power supply. It is fed from the outside aerial and
screens are not included.
Terry Cassell of Microtext explained that syn-up to 16 channels are available.
Conspicuous by their absence are tuning knobs - the unit is totally self-tuning. Once the initial tuning procedure has been implemented, the settings can be saved to disc or tape. From then on typing RUN"teletext will put the first teletext screen up in a matter of seconds.
If used alone, the adaptor must be fed from the Video Out socket of a video recorder, and the teletext channel is selected by the recorder's channel selector. If a video is either unavailable or undesirable the tuner unit must be used, in which case an aerial splitter will be needed if both teletext and TV are needed at the same time. This can be bought from most TV shops for £2 to £3.
exceptions - subtitles and double height halfchronisation of the two signal sources - the CPC for the teletext and the TV for the picture - would be either impossible or prohibitively expensive. He also pointed out that since most people would not be using the adaptor with a TV but with a monitor, subtitles would not be needed.
On the double height half-screen - a facility for those with poor eyesight which displays half the screen at a time in double height characters -Terry said that since most users would be sitting close to a monitor and would be quite used to reading monitor-type text, this facility would also not be needed. I agree on both counts.
There are a couple of other omissions, the alarm facility for one, but again they have no real use in the computer set up.
I was a wee bit disappointed when I saw the on-screen character set. At first I couldn't understand why Microtext had chosen to dispense with the CPC character set in favour of an inferior design.
The reason is that teletext uses eight on-screen colours, whereas the CPC will allow only four colours in Mode 1, so Mode 0 had to be used.
The characters were designed using the larger Mode 0 pixels, yet still occupying Mode 1 screen space. The resulting set can never be as good as the normal Mode 1 set, but is quite adequate, and you soon get used to it.
Having brought up the subject of colour, I should mention that I have tried the adaptor on a green screen monitor, and although some colours are rather dull - the brightness needs to be turned up -1 didn't find any colour mixes that make text disappear from view.
I can't say it will never happen - in fact Phil's first law of wires and teletext adaptors, which states that "If it can, it will", almost certainly applies - but the chances of finding disappearing text, or rather not finding text, seem to be slim.
So we've seen how things compare with a teletext TV, but this adaptor is connected to a computer, and the computer has memory in which to store the Teletext data. If the data is in memory, it can be saved, loaded, printed and accessed from another program. Now we're reaching parts that other teletext devices cannot reach.
OK, so we can't mix pictures and text. But we can do a whole lot more. By pressing S and entering a filename the screen currently on display will be saved to disc or tape. Conversely, pressing L and a filename will load a screen. Pressing P will send the screen to the printer.
Telecred, the teenage magazine on Ceefax >>
A special printer driver is available, at no extra cost, for the DMP1 printer. All good stuff, eh? And there's more.
The software has been designed to allow easy access to teletext from within a computer program with the adaptor's documented machine code subroutines. And it is quite conceivable that a program could be written to analyse such things as stock market trends, weather cycles and football results. Two examples of Basic programs that make use of the software are given in the manual.
The teccy bit
One thing I would like to dispose of straight away is the fact that the adaptor does not rest on the desk when plugged into the computer. I have raised this subject in a previous review of the Microgenic Systems ROM board, when I wondered if a clumsy person might manage to break
the computer's main board by accidentally pressing down on such units.
The answer is no. I did a test with a 464 main board and a home-made ROM board. The only thing to break was the ROM board's edge connector, which broke in such a way that it could still be used.
Furthermore, the weight I had to apply before it snapped was enormous - about equal to a falling adult using the unit to stop the fall. I am now convinced that the risk of damage to either computer or add-on by this "hang it on the back" method is so tiny as to be not worth considering.
The alternative would be for manufacturers to make different sized models for the different sized CPCs, like the Dk'tronics stuff, and that would put up the cost.
The teletext system uses a 1k screen. Even though memorywise this is not very much, the adaptor has its own 2k RAM chip built into it for screen storage. I presume this is to leave the CPC's memory free for those massive teletext accessing programs that we'll all be writing.
Each screen uses just 2k of disc space, allowing 64 screens to be saved on one side of a disc. 89 screens, did I hear you say? No way. Only 64 entries to a directory, chums.
The printed circuit boards of both units have good ground plane areas, aiding reliability, and make use of the 74LS series logic chips to avoid any user damage which might be caused by static electricity.
A lot of care and attention go into the artwork and stories on Oracle 's kiddie pages
I was pleased not to find a ROM in the adaptor, which would use up a valuable ROM slot. Not because the use of slots by add-ons is undesirable, quite the opposite, but because when used with the tuner, channel settings for a particular area have to be tuned and saved to disc or tape. Since some of the software must, therefore, be on disc or tape, it is better that all of it is.
The two metre video lead supplied with the adaptor will fit the usual BNC Video Out connector, which looks a bit like the metal part of a small bayonet type light bulb. Alternative connectors are available from Microtext at no extra cost, as are longer leads at 50p a metre. The tape software is easily transferrable to disc, but it can be bought supplied on disc for an additional £5.
I would like to sum up both negative and positive aspects of the two units, but I can't really find much in the way of negative ones. I've never tried to design a Mode 1 type character set with Mode 0 pixels, so I dare not suggest that it could be better.
The omitted teletext features are not really desirable anyway in a computer setup, and I can't even quibble at the price. At £74.95 the adaptor unit is cheaper than the £80 difference between a standard 22in TV set and the same set with teletext.
Although it takes a little time to turn the computer on and load the software, the additional features provided by Microtext's Teletext Adaptor, such as printouts and saving screens, are a great improvement over the old fashioned method of receiving teletext through a TV set.
The tuner unit is slightly different. It is neat, compact and performs its task admirably. It is also £49.95. These days second-hand video recorders are going for that sort of price. They are not as neat and compact, and they will not last forever, but they do have suitable tuners. Food for thought?
Quick tip: A video's recording quality tends to deteriorate before its playback quality so, if you're buying one, see it record.
Finally, I should mention that I have found one ROM with which the system doesn't fully operate. This is not a fault of either ROM or teletext adaptor, but a common occurrence when different programs want to use the same area of memory. The problem is easily solved by switching the ROM off.