One of the advantages of living in England, Home of Sinclair Research, is that we get to try out some of the “extras” before anyone else. Here are some of the things that may cross the Atlantic from England for the ZX81.
An exciting new development for the ZX81 enthusiast is an alternative keyboard to replace the “touch,” but not very sensitive keyboard. There have been a lot of complaints on this side of the water that the keyboard is slow and difficult to use because of the lack of “moving keys.” This new “KLICK” keyboard from Kempston Electronics (60 Adamson Court, Hillgrounds Road, Kempston, Bedford, England) is the same size as the Sinclair, but 1 cm taller. The keys are made out of proper keyboard switches and have the appropriate legends stuck on top. The layout of the keys is also the same, and there is even space for a repeat key. The keys move under your fingers, and it is very light and easy to use. Connection to the ZX81 is made by plugging two plastic cables into the keyboard sockets instead of the Sinclair keyboard. The Sinclair keyboard has to be first removed by peeling it back (it is only a few millimetres thick) and then after undoing the screws on the base removing the keyboard “tails” from the sockets. The result is beautiful to look at as well, as it is finished in black to match the computer. The cost including U.K. VAT at 15% is £27.20.
The same firm also has a keyboard beeper and repeat key modules which fit inside the computer under the keyboard.
A keyboard beeper that does not require any soldering at all is made by Fulcrum Products (Hillside, Steep lane, Findon, Worthing, West Sussex, England). This comprises a printed circuit board which is small enough to fit inside the ZX81/Timex underneath the keyboard or even under the computer’s own printed circuit board. The hole connections within the computer are made by inserting spring clips into the holes which are already plated to carry the circuit from one side of the board to the other.
The connections to the keyboard are done by removing the keyboard “tail” from the socket on the computer board (only one has to be moved) on to an identical socket on the beeper. A keyboard strip containing the same sort of metal strips is then plugged into both the keyboard socket and the beeper. This is all the connection required. It can be easily removed if the computer has to be sent back for repair.
It beeps whenever a key is pressed including all the modes (G, F, L, and K). It also works on all the keys when the SHIFT key is held down. It is a very good method of making sure that the computer has registered the key press on Sinclair’s thin keyboard. The cost of the board is £8.95 including VAT.
While we are on the subject of solderless additions, how about a RAM board which fits inside the ZX81 via a set of screws (no RAM pack wobble here) and can have up to 16K of semistatic memory on it? The board is called the INCREMENTAL RAM board and is made by East London Robotics (Finlandia House, 14 Darwell Close, London E6 4BT). The board costs £13.23 for the 16K board and £4.93 for each extra 2K of memory required (one plug-in chip).
The board uses CMOS 6116 RAM chips which can be purchased in the USA. Being semistatic CMOS they take less power than 16K dynamic RAMs and can be powered by batteries to keep a program intact when not in use. They are also more reliable than dynamic RAMs which rely on the REFRESH signal. The increment board is easy to fit with brass screws through the plated holes on the printed circuit board to make the connections. It can even be removed with no trace when sending the computer back for repair. There is also the advantage of not having a wobbling RAM pack blocking up the expansion port.
If, however, you decide later that you want to use more memory, the increment RAM can be moved to any position in memory to give increased Basic memory from 32K upwards or from 8K upwards for running machine code programs in, etc.
Another basic problem with the Sinclair/Timex is the amount of glare that you can get using an all white screen. Most computers work in reverse to the Sinclair and PRINT on a black background, thus saving eye strain. Now a device is available from D. Fritsh (6 Stanton Road, Thelwall Warrington, Cheshire, England) which will reverse the TV screen at the flick of a switch. This inverse video module (£7.50) sits on top of the ULA chip inside the computer, stuck there by a piece of sticky tape. The only connections required are to the video lead and to the power (+5v and 0v). The switch is already wired up.
The instructions are superb, and they even include a template for drilling the hole for the switch. An added bonus is that it improves the “crispness” of the display and stops graphics, for instance, from looking fuzzy.
If I seem to be a hardware fiend, it is only because the best programs over here are in machine code and some of them will not operate in the USA without modification. This is because they do not use the Sinclair ROM routines to put out the TV picture, but write their own in order to get fast graphics. The TV system over here is 625 lines PAL on the UHF band. The USA frequency is VHF NTSC 525 lines and is totally uncompatible.
One of the programs in Basic that I have is a word processor by Asher & Kuehn (60 St. Lenonards Gardens, Heston, Middx, England) with two forms called ZTEXT and LTEXT. ZTEXT provides only CAPITAL letters while LTEXT gives both CAPITAL and lower case letters on the printer. Both are on the same cassette for £6.
There are two modes: write text T and edit text, the second giving all the functions of insertion, deletion of lines of text, searching for a specified word or phrase, replacing the found word with another or printing it out on a Sinclair printer. Also it can be used to “mail merge” letters by indicating on the standard letter where words should be different on each letter (Name, Address, etc.). The program then stops to allow you to insert these details and ENTER will carry on the printing. The number of variations of setting the page width, number of lines, tab, and other formatting commands are available as a dot followed by the code letters. It is very good, given the restrictions of a 32 character screen, but does not have the ability (in the case of LTEXT) to display lower case or all the punctuation marks. These are usually indicated by INVERSE characters on the screen. Altering the program to use a real printer can be done.