DK'Tronics Light Pen MK2/3

Sinclair User

Stephen Adams

IMPROVED LIGHT PEN Among hardware releases promised by dK'tronics is a new version of its Spectrum light pen. The pen is supplied with software for both 16K and 48K versions and is a vast improvement on the old version. As with the majority of light pens, there is an interface which connects to the computer, in this case the inevitable black box which fits into the user port and which is dead-ended, and a pen which plugs into the top. The interface contains a minimum of electronics; all the work is performed by the software. A TV picture is made up by a spot of light which zig-zags down the screen. By timing how long it takes from the start of the scan to when it is picked up by the pen, the software can determine the position. The instructions show how you can use it in your programs to choose from a menu and give you the address of the 96 bytes of code needed. In addition, the software contains a drawing program which can be used to create pictures. The program offers a number of options to draw lines, arcs, boxes and circles, fill areas, change colours, insert text and LOAD and SAVE pictures to tape. On a 48K machine up to four screens can be kept in memory at once and then recalled, singly or one after another, to provide limited animation. The acid test of a light pen is when trying to draw freehand and that it does remarkably well. The straight lines are straight and the pen draws where it is pointing. The only disadvantage is the lack of error-checking on some of the commands, such as when drawing an arc which goes off the screen when you are dumped back into Basic. You can return to the picture without losing it but it is annoying. If you are looking for an accurate light pen you could do far worse than this pen which sells for £19.95, from dK'Tronics Ltd, [redacted] and computer shops.

Sinclair User

Stephen Adams

WRITING IN LIGHT MAKES INPUT EASIER The Spectrum Lightpen by dK'tronics is a kit consisting of a tape, light pen with a 3.5mm plug on the end and a black plastic box. First you run the tape into the Spectrum; the 48K side unfortunately has the 16K version on it and vice versa so if you get out of memory, pull out the plug and start again on the opposite side of the tape. The program loads a Basic instruction program which then loads a machine code program above RAMTOP. All goes well to that point. The instructions on the screen then warn you to plug the light pen via the control box into the computer. The power lead must be diverted through the box when you power-up the computer but the light pen must be disconnected while LOADing or SAVEing. The list of instructions is vast and all letter-coded. Choosing a letter from the menu gives the instructions associated with that letter. Having gone through the instructions, you have to set up the delay for the screen. That is the first bit of machine code and immediately crashes the program on the 48K version. On the 16K version there is no list of instructions - they are listed in the manual. The light pen works well; it reacts with the instructions satisfactorily. The position of its reaction can be adjusted up or down by a knob on the top of the unit. That varies the pulse sent to the EAR socket by the black box. dK'tronics light pen costs £21.20 and is avaibble from [redacted].