A CHARACTER generator is available for the ZX-81 for £19.95. It can be fitted beneath the keyboard or outside the ZX-81 and requires only four soldered connections to the printed circuit board.
A character generator is a device which allows you to design the character set you want to see - Space Invaders and lower-case letters being favourite examples. The characters are stored in RAM at 15872 so they can be PEEKd and POKEd.
A three-character REM statement is all that is required to exchange your characters for Sinclairs. The character board can be obtained from D Hutchinson, Harlow, Essex.
A LOADING aid for ZX machines is available to help you find the correct level of your tape recorder. It consists of a small black box with two LEDs on top which will glow together when the correct level is reached.
The device plugs into the EAR and power sockets of the computer with the power pack/tape leads plugging into its sockets. The loading aid is different for the ZX-80, ZX-81 and Spectrum, so specify when ordering. The loading aid is available at £11.95p from Fulcrum Products, Worthing, West Sussex.
PRINT-N-PLOTTER has produced a plotter for the Spectrum so that you can transfer pictures from magazines to the TV screen, making the most of the more than 45,000 dots available. The pad has a set of seven coloured pens and has 50 pages of PRINT squares and 50 pages of hires squares to fill in.
Each page also contains six squares with which to design your own characters. A demonstration tape of what it can do is available for 60 pence. The Spectrum jotter is available from Print-n-Plotter Products, London SE1.
ABACUS ELECTRONICS has improved its tape lead controller to work with the Spectrum. It uses a switch to disconnect the correct tape lead when SAVEing or LOADing, instead of having to pull out the plugs. It can also be used as an amplifier to produce BEEPs and keyboard clicks which are easy to listen to via a built-in loudspeaker.
The firm also produces a DIN plug version for use on tape recorders without 3.5mm. jack sockets.
The controller costs £14.95 from Abacus Electronics, W. Glamorgan.
THE ZON-81 is a three-channel mono sound box which fits on the back of the ZX-81 and soon the Spectrum. It is a I/O device and contains its own loudspeaker and volume control. It can be programmed to give a wide range of sounds, from gunshots to an electronic organ.
There is also a noise generator included in the AY-3-8912 chip. The box is powered from the computer and is driven via two machine code routines - nine bytes in all. The cost of the unit is £25.95 from Bi-Pak, Ware, Herts.
IF YOU WANT a permanent way to store your programs but still change and correct them, why not try a Memic-81? It is a battery-backed RAM box which fits on the back of a ZX-81, so that when you switch off the computer the memory is not lost. It is also preserved during NEW and LOAD.
It is in two versions, 2K and 4K, but can be expanded to 8K by adding more chips. The RAM pack appears in the 8K-16K space on the memory map but can be moved to another area if desired.
The Camel products range also includes a 8-bit port and a 8K ROM/ EPROM board. The price of the Memic-81 with 2K of RAM is £28.70; the 4K version costs £34.45, the port £14.95 and the ROM pack £17.19.
Camel products can be obtained from Cambridge Microelectronics Ltd, Cambridge.
A KEYBOARD REPEAT which works like that of the Spectrum on a ZX-81 will work with any keyboard, as it is soldered to the ZX-81 beneath the keyboard by nine wires. It is also small enough at 4cm. square to fit under the PCB if you already have something there.
Every key will auto-repeat if held down for more than a second, including the SHIFT keys, and if the soldering worries you the company will fit it to your ZX-81 for £2.50.
The Auto-Repeat (built) costs £5.50 inc. VAT and post from Kempston Electronics, Kempston, Beds.
AN INGENIOUS device which suits anyone who needs to design their own characters is a plastic wallet with two 8 x 8 grids marked with numbers around the edge.
A set of magnetic black squares can be put on to the white squares and moved about without fear of them falling off. After a character has been worked-out the numbers of the squares can be fed into the computer to form each line of the character.
On the Spectrum they can be fed in as binary using the BIN function or on the ZX-81 using the decimal equivalents read from the pad.
The characters can be designed quickly and easily without having to have the computer on. They can also be designed in a car, bus or even in the bath. Two grids are included so that bigger designs can be made by using more than one character. The MCP can be obtained from MCP Co, Harrogate, North Yorkshire for £2.95.