John Dawson argues the case for portability. He shows that the idea of a micro in a suitcase – or in this instance, a camera case – need not be the preserve of relatively costly machines such as the Osborne.
Portability and communications are becoming important trends in microcomputing. The Information Technology revolution that is going on at the moment will create a demand for information away from orthodox outlets such as Telex machines, VDUs attached to mainframe computers and static microcomputers.
The Osborne 1 microcomputer exemplifies one approach to portability – considerable processing power with large-scale data storage in a man-portable pack. In the early photographs advertising the Osborne 1 a comparison was made between two men, one with an ordinary briefcase containing sandwiches and papers, and the second with the computer. Leaving aside the advertising claims I was always fascinated by the white knuckles of the man carrying the computer – just how much did it weigh?
The other approach is a genuinely portable terminal with limited storage but with the capability to access huge databases by way of the public telephone network. The IXO telecomputing system described in the April 1982 edition of Byte magazine is a fine example of the shape of things to come.
Pocket terminal
The IXO terminal is about 6in. long by 4in. or 5in. deep, is truly user-friendly, with excellent ergonomic design, and has a single-line liquid-crystal display with a QWERTY keyboard. There is a telephone Modem inside, good security protection to make it difficult for an unauthorised person to use your terminal, or their own, to access one of your files on the main computer, and the protocol you require to access a database can be stored automatically in CMOS RAM.
EPSON is launching the HX-20 in the States, a portable computer working on Nicad batteries with a four-line liquid-crystal display 24 characters wide which will display upper and lower-case letters as well as the rest of the ASCII set.
These new computers and devices are not just marketing gimmicks. The ability to utilise the power of a computer in several places has already been shown to be very valuable. For example, Government officials with terminals coupled to a main computer by an acoustic coupler have been helping farmers in the U.S.A. for years.
Doctors in this country have used portable data capture units for analysing the electrical activity of the heart for some time, and when you couple a computer, rather than a dumb terminal, to a central store of information, the sky’s the limit.
Having just finished writing Asimov, a word-processing package for the Tangerine Microtan, I wanted to be able to work on papers and reports both at the office and at home. I could have bought another Microtan solely for the office and it would have been fixed there with the same trailing wires; but at the same time someone at work said that she wanted a word processor for articles, press releases and a book.
It seemed a good opportunity to share the use of a portable word processor. The main photograph on this page shows the result of a weekend’s work putting a new computer into a portable case.
When I planned the project it seemed reasonable to assume that a television would be available wherever the machine would be used. There is a TV in most homes, colleges, conference centres and hotel rooms for someone who is travelling. Consequently, there is no VDU built into the unit.
Railway work station
The Micro that fits so neatly into a case is mains powered but could run for several hours off of a battery pack.
If you want to use it on a train, you will need a battery pack for the computer, like the Osborne 1, and a battery-powered TV. Printers are still expensive so I decided that it would be an acceptable compromise to prepare material on the portable work-station, store the text on to tape and then print the text on my own computer at home.
The text would be transported either as a finished cassette tape or electronically along a telephone line. This is essentially the same method as a remote work-station in an office preparing text and then printing the final document on a central printer.
I like the Tangerine keyboard very much and I wanted to incorporate it into the unit without modification, so the computer case had to be wide enough to take the keyboard in its steel plinth. After rummaging through several iuggage shops I found a version of the case I finally bought but it seemed overexpensive.
The same case is sold by Dixons camera shops as the Chinon Corniche, costing £29.95. The Corniche is about 17in. wide inside and is 5.25in. deep, about 0.75in. taller than the Microtan boards.
Asimov can manipulate about 7,500 words when used with a fully-expanded Microtan – or approximately 900 words with a full Tanex board – and I wanted to leave room for a Tan RAM card in addition to the central processor unit and the several Tanex boards.
Furthermore, Microtanic Software which is marketing Asimov, is also bringing out a high resolution board that will give a screen 64 characters wide by 25 lines and I wanted to take account of that in the space left for future expansion.
The case shown in the photographs has a number of features that are particularly well suited to this purpose. It is constructed out of plywood with a thin aluminium veneer on the outside and is quite rigid. Plugs and sockets can be mounted directly on to the case and the metal skin can be connected to the mains earth without difficulty. The plywood is strong enough to support a surplus mains power pack for the computer. Indeed, fixing the power pack in three places to two different panels strengthens the case.
The 5V PSU mounted inside the camera case.
I stripped out the fancy foam padding and ribbed side decoration and when I had secured the power-supply unit, I played with the computer boards, the keyboard and the tape recorder for some time.
Was there an advantage in having the boards lying flat, and stacking one on top of another? What effect would that design have on the ventilation of the boards? Did the keyboard fit over the tape recorder and, if so, was that an efficient use of space, leaving room for the connecting cables?
What about electrical safety? Could I bring mains power round to the right-hand side of the case, close to the signal wires, without inducing mains noise and corruption on the cassette and keyboard leads?
The connections to the word processor.
I only constructed the computer after a good deal of thought. Destroying the guarantee on £30′s worth of case by drilling holes in it is always rather an anxious business, but it turned out well.
The keyboard rests on two side steps when it is in the case and the steps are deep enough to support the keyboard sufficiently clear of the National Panasonic Slimline tape recorder to store some cassette tapes between the two.
The mains input is on the left-hand side of the case and a lead is taken underneath the left hand step to a neon light on the front surface. There is no on/off switch; when you plug the computer in, it is on.
I completed the mains wiring before doing anything else, bringing a lead out to the right side for the tape-recorder power. The next step was to fit the keyboard and measure the space remaining for the computer boards. I used a spare mini-motherboard and mounted the CPU and Tanex cards upright and as close to the partition between the keyboard and the rest of the case as possible.
Screen expansion
By hand-wiring a bus to two or more Eurocard sockets, I expect to be able to fit the TanRAM and big screen boards in the space at the back of the case. The aluminium panel separating the power-supply unit from the computer is bolted to the back of the case and to the unit.
It is carefully earthed both to act as a Faraday screen and to protect the computer should a mains lead come astray from the input to the power-supply unit.
The 16-pin dual-in-line plugs and sockets were never designed for frequent connection and disconnection; if you do not believe me look at the amount of metal in the Military-Specification socket shown in photograph 9 and remember that it was designed to cope with salt water, mud, vibration and parachute drops.
Accordingly, I cut the keyboard cable on the Microtan and used a 25-way D plug and socket to connect the keyboard to the computer. Radio Shack has plastic D plugs and sockets with fittings to couple directly to ribbon cable.
The clamp on the back of the plug is comparatively fragile and it is easy to break the side arms that hold the back in place. The chrome bar on the right-hand side of the case is intended to protect the sockets from damage when the computer is moved.
Before doing anything with the computer I switched on the power-supply unit and checked the mains volts and the output volts. Remember to switch off before going anywhere near mains voltages — at 230V AC, the mains can kill you.
If you want to check mains voltages connect the multimeter and then switch on to obtain your reading. If it is impossible to do that then at least keep one hand in your pocket which will substantially reduce the chance of your receiving a shock through both hands across your heart.
The output socket from the modulator on the Microtan protruded too far and I removed the socket, soldering a coaxial lead directly to the unit. When I plugged the central-processor unit board into the motherboard and switched on, it worked. When I plugged the Tanex board in beside the CPU card and switched on it functioned until I added a full set of RAM chips.
Then it worked for just half a second before failing completely. There was no time to see an organised pattern on the VDU and then the screen went blank. I checked the Tancx board, which I had made from a kit, and resoldered many of the joints, looking always for thin whiskers of solder that might short out the power supply. Nothing obvious, even under a magnifying glass.
Eventually I connected a low resistance across the power-supply unit with a multimeter in series to measure the current the unit would put out before it shut down. After adjusting the current limiting variable resistance to allow the supply to give at least 1.5A, I reconnected the computer and the Tanex boards. This time it worked; it was just coincidence that the difference in current drawn by the Tanex board with the full complement of RAM was sufficient to shut down the power supply unit.
Conclusions
- The whole case weighs about 10 kgm. when it is packed.
- Asimov is easy to use, and the VDU sits comfortably on top of the computer case – the facility to do work on a word processor and to take the machine with you at night or at the weekends is splendid.
- If flat screens are developed to the stage where they are cheap and reliable in the near future I shall be tempted to mount one in the lid of the computer case so that I can write on the commuter train.
- The final touch would be an acoustic coupler to transmit and receive text down a telephone line.
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Contents and Editorial for this issue of Your Computer
Tags: 1982, Asimov, Chinon Corniche, Commuting, Computers, John Dawson, Kit Building, Portability, Retro, Technology, Your Computer
