Tandy TRS-80 Colour Printer

Personal Computer News

Bill Davies

TECHNICOLOUR TANDY Getting bored with the old black-and-white? Bill Davies discovers a colourful alternative. A price breakthrough by Tandy is an event in itself, since Tandy watchers have always been aware that the Fort Worth-based computer/electronics company has never attempted to break into the cut-throat low cost market. At £600 the new Tandy CGP-220 seven colour ink Jet printer is very competitively priced. FIRST IMPRESSIONS The printer comes in a substantially protected box with polystyrene and polythene covering. Opening the box the first surprise is the new colour scheme which has been adopted by Tandy for all the new product range. Instead of the traditional black and silver, the CGP-220 is housed in a cream plastic case. Powering it up for use provided no problems either, since Tandy now ensures that all products are fitted with a three-pin 13amp plug to conform with British standards. Other manufacturers please note. DOCUMENTATION Here I'm afraid Tandy let me down. In my experience Tandy computer manuals are generally some of the best on the market, but the manual with the CGP-220 is somewhat lacking to say the least, it's laid out and printed in the normal Tandy printer manual layout, but bearing in mind the revolutionary design/concept of the printer I was disappointed to find there was little in it that actually describes exactly what the printer is and does. It took considerable time and effort to discover the method of printing. Briefly the printer is a form of spark jet printer. The ink is produced in minute quantities and transferred to the paper by means of a fast high ignition spark, each dot of the matrix requiring a separate function. To understand how the colours are reproduced one has to step back into basic physics. In television and monitors, colours are produced by mixing light rays. In this system - commonly known as the RGB method - red, green and blue light rays are projected on a surface and mixing these three colours generates all others. A second method is based on the mixture of pigments such as ink or paint. In this method, the colours yellow, magenta and cyan are mixed in different combinations to produce other colours. The CGP-220 uses the second method. The built-in software in the printer converts what the monitor sees as RGB into mixtures of the coloured inks available, it does mean that you probably don't have the full range of colours available that you would expect to find on your television set, but it should be a close approximation. GETTING STARTED Familiarising yourself with the machine is the first thing to do. Although the ink packs should already be inserted when you get the machine, they don't really cause much of a problem. You should have two packs both the size of a packet of cigarettes. One contains black ink and the other has yellow, magenta and cyan. They are contained in rigid containers and the ink is sealed in airtight bags. With the power off they are inserted into a small drawer located along the bottom front of the machine. After they are installed, you are warned not to take them out until they are exhausted. Being the inquisitive type, I did, with disastrous results - ink all over the place. To protect the ink supply during transportation and lengthy periods of inactivity there is a lever on the top of the printer which can be positioned to seal off the supply. The printer takes either roll paper or single sheets - there is no tractor feed. Again inserting paper is no problem. The controls for the printer are loCated on the front. They are touch sensitive for 'restart', 'feed' and 'on/off line'. Alongside are three LEDsready, alert and power. When you turn the power on the red 'alert' light blinks for about ten seconds as the ink supply is made ready. The red alert light also comes on when you run out of paper or when the printer goes off-line for any reason. Once the situation has been rectified, pressing the restart key should set the printer off again. On the top left of the printer alongside the paper platten is a green lever which provides three functions. Locking the carriage for transit, capping and uncapping the ink nozzle, and a pump to provide a better ink supply. After loading the paper it is advisable to check the ink supply and ensure that all colours are working. Pressing the FEED button immediately after unlocking the carriage should produce a horizontal bar. There is also a self test function which prints out all the alphanumeric symbols. Each line is printed in a different colour. The next step is to connect it up to the computer. The CGP-220 is provided with serial and parallel connections and there is a baud selection switch for 600 or 2400 baud rate for the serial interface. Since I already use a Tandy printer I had the necessary cable to hand, but it is necessary to watch the pin connections on the parallel cable, since the BBC and the Tandy system differ on the location of two pins. Numbers 10 and 11 have to be changed round, otherwise busy and acknowledge get mixed up. IN USE The first thing you notice is that the printer is exceptionally quiet, although the print head appears to do an awful lot of work. Each row of dots is printed in a separate operation, which means that for one line of type the print head has to make seven passes over the paper to produce the text. The computer communicates with the printer with a series of control codes. These codes are used to tell the printer exactly what you want it to do. As on most printers the information is sent as numbers between 0 and 255. A control code would be used to change the print size, or a linefeed or to change the colour of the text. Normally you would send two sets of codes to the printer - 271, known as an ESCape code, followed by two other digits for the actual function. The CGP-220, being a colour printer, obviously requires slightly more information, so you have to send three sets of digits to it when changing colours. Each colour has been allocated its own number between 48 and 55: black, red, green, yellow, blue, magenta, violet, white. So to change the text from black to red, for example, you would have to send the code 27 (ESC), 84 (telling it you are changing colour), 49 (red). These codes can either be inserted into the text if you are using a word processing program or into the Basic program if you are writing a program which requires colour changes. The CGP-220 will print either standard or elongated characters. These are selected using control codes, but the printer defaults to standard text character code on power up. Although the printer comes with an American character set, the European character set can be selected by programming the appropriate control codes. Tandy say the printer's biggest selling point will be its ability to provide colour printouts of graphics, bar charts, graph tables etc. I have no doubt that this is true - the machine is certainly capable of producing a variety of colours. But the manual is extraordinarily vague about the actual mechanics of it all. As you would expect, many of the instructions in the manual are aimed at the Tandy computer owner, and all the demonstration programs use the LPRINT instruction. The print speed is very slow - claimed to be about 37 cps. This does mean that anyone wanting to use it to print text will have to wait a long time, and because there is no built-in buffer it will tie up the computer for really long periods while it is performing its tasks. VERDICT This printer provides colour printing at a price that many people who may have shied away in the past could well afford. Like all Tandy printers it is fully compatible with most micros on the market, and I am sure will be of great use to educational establishments and businesses who want graphics work carried out, but feel that the very high cost of the other colour printers on the market is not worth it. But for the home user it is an expensive luxury, unless you are really keen on producing colourful graphics dumps. There is also competition in the form of the Seikosha GP-700A which offers seven-colour print at a lower price - under £500.

'The printer is exceptionally quiet... but slow'