THE TELESOUND 82 audio modulator by Compusound can make a great difference to the Spectrum. The Spectrum has a built-in loudspeaker but the reproduction can be so faint that it cannot be heard except in a very quiet room. The Telesound 82 amplifies the sound by sending it with the video signal to the TV set, where the amplifier and loudspeaker can make that small sound deafening.
All sounds produced by the loudspeaker can be reproduced, from the BEEP command to the click sound emitted from every key. There are only two connections to make inside the Spectrum, one to each of the two wires going into the video modulator, and that is achieved by crocodile clips.
The jack plug provided is then plugged into the EAR or MIC socket and the unit is in use. You can obtain the Telesound 82 from Compusound, Worcs., price £9.95.
HAVEN HARDWARE has produced a colour board for the ZX-81 which can provide up to 16 colours for each of the character squares. The colours are POKEd into the top part of the 16K memory into 1K of on-board memory which retains the colour.
The position in memory varies with the movement display file and so must be calculated every time it is POKEd.
Only one internal connection has to be made, as all the other signals are obtained from the expansion connector. More details can be obtained from Haven Hardware, Cumbria. The cost of the colour board is £39.95 as a kit and £49.95 as a ready-built unit. All prices include VAT and postage.
D FRITSCH has produced a video inverter kit for the ZX-81 which rests on the ULA and it requires only four connections to the ZX-81. Two of those connections are made to the power supply and the other two are obtained by soldering a wire to each side of a break which is made in the video lead going into the video modulator.
The video signal is also made sharper on the TV screen by the use of an amplifier instead of the usual integrated circuit gates. A switch is provided - with a template for cutting the hole in the back of the ZX-81 - for switching between normal and inverse video as the tape LOADing and SAVEing cannot be seen so clear in inverse video.
The price in kit form is £4 and for £7.50 the unit will be fitted to your ZX-81 for you, including VAT and postage. Contact D Fritsch at Warrington, Cheshire.
Lander Micro Systems LMX EPROM programmer.
LANDER Micro Systems has produced an EPROM programmer for the ZX-81, called the LMX. Using a printed circuit board which plugs into the back of the ZX-81, the programmer can be used as an EPROM card containing 2K of pre-programmed memory (ROM) or to reprogram a 2716-type EPROM.
To re-program an EPROM it first has to be treated with ultra-violet light to clear all the bits to 1s. It is then inserted into the board and a 36V supply made up from four PP3 batteries - not provided - applied.
A special keyboard overlay and program tape is provided which will allow you to step through the addresses in the EPROM and change them. The device covers the whole of the 8K-16K memory space. The LMX system as a kit costs £17.50 including post and VAT from Lander Micro Systems, Romford, Essex.
ORME ELECTRONICS has a 2K EPROM which contains a Toolkit for a ZX-81. The EPROM card which takes the EPROM can be bought separately from the EPROM at £9.25. The card contains one socket for the EPROM and an extension board to plug in other equipment like the 16K RAM pack at the back.
The Toolkit contains routines such as renumber, block delete, hex-to-decimal conversion and vice-versa, READ-DATA and load machine code from tape.
The EPROM also contains a fast version of the games of Life and Breakout. All this costs £9.25. Contact Orme Electronics at Camborne, Cornwall.
CUSTOM CASES packs all your ZX-81 or Spectrum equipment into one portable briefcase, 19in. x 14in. x 4½in. The case is filled with polyurethane foam and has cut-outs for the computer, printer and RAM pack and, when it arrives, the ZX Microdrive.
The foam is covered with a red nylon finish and looks very attractive as well as useful in the aluminium-framed, plastic-covered briefcase. The case is lockable and keeps the ZX system neat, tidy and ready for use at any time by plugging-in the TV leads and the power supply.
The cost of the case is £ 36.95, including VAT and postage, from Custom Cases, Herts.
AN RS232 interface for a printer is available from a new company specialising in ZX equipment, Cobra Computer Services, at a cost of £30. It works from the ZX power pack and can be used with most RS232 printers to produce graphics and text.
Cobra is also offering a business consultancy service for those who want to use a ZX machine on the basis of a computer system. The company will be able to put together packages for users involving disc systems, hi-res graphics and printers at low cost. Contact Cobra at London N1 (mail order only) for a brochure, enclosing a SAE.
EAST LONDON Robotics has produced a 64K add-on RAM board for a 16K Spectrum costing £50. It fits inside the Spectrum in the sockets provided for the Sinclair 32K board. The RAM is in two banks of 32K and is switched over by an OUT instruction. LEDs indicate which block is in use.
Contact East London Robotics, London, for your 80K Spectrum.