Graphics digitizer

for~text or static pictures. Points are drawn on a 1024 × 1024 matrix and refreshed 30 times/see, in the non-store mode. In the store mode they remain visible for 15 min. The VPI 5 (m) can support up to eight independent display terminals. The VP (b) is an oscilloscope display which can be expanded, compressed, centred or shifted and can work with a light pen. The VP15 (c) is an xy display sytems refreshed 30 or 60 times/see on a screen 17 x 23 cm. (Digital Equipment Co Lid,

Arkwright Road, Reading, Berkshire, England). MAGNETICALLY CONTROLLED D R A F T I N G CABLING. The drafting heads of the Xynetics drafting system (shown here) rides on an air bearing and is controlled by two permanent magnets arranged at right angles and with an electromagnet wound round each end. The platen is criss-crossed by strips of non-magnetic material, dividing it into squares. This system eliminates all mechanical control methods and permits drawing speeds of up to 100 cm/s repeatable to 25Fm. The head moves continuously, not in increments. The Xynetics drafting table comes in three models, the biggest of which is 140 × 220 cm. A variety of heads can be fitted, including a photo-exposure head and a scribing tool. The drafting system works with an ASR33 teletypewriter, through which the operator controls scaling, origin, speed and rotation of drawings and a magnetic tape controller and paper tape controller. There are a variety of other systems. (Xynetics Inc, 6710 Variel Avenue, Canoga Park, California 91303, USA. Intertrade Scientific Inc, 64 High Street, Pinner, Middle-

sex, England). G R A P H I C S D I G I T I Z E R . Measuring areas up to 150 cm × 200 cm and a measuring accuracy of 100/~m are the characteristics of the Autotrol Model 3990 graphic digitizer. A precisely ruled glass scale enables accurate co-ordinate

readings to be taken and areas and volumes can be calculated. Variable scaling is incorporated and the system also incorporates a third co-ordinate for photogrammetry. Outputs are to paper tape, magnetic tape, discs and punched tape and also to special interfaces. There is an optional grid round-off to between 25Fm and 250/.tm. (Autotrol Cpn, 6621

West 56th Avenue, Arvada, Colorado 80002, USA). C L E A N H I G H - S P E E D D R U M PLOTTER. The Model 462 drum plotter

reaches 5 m/s in less than 30 m s and can maintain a resolution of 50/zm and a repeatability of 125/zm at this speed. Our photograph shows the drum plotter, comprising a model 62 drum (left) and a series 400 controller on the right. (Gerber Scientific Instrument Co, 83

Gerber Road, South Windsor, Corm, USA). HIGH-SPEED R E M O T E PLOTTER. At 2 600 increments per second, each increment being 0.063 mm, the 1136 plotter from CalComp can move 16cm/s axially, 23 cm/s diagonally: resolution is 0.625 cm. The pen-holder can take up to three pens, ink or ball-point and with variations of line width and colour. The Model 900 controller used with the 1136 drum plotter and the model 937 magnetic tape unit complete the system. A graphics software cartridge fits into the controller, the particular cartridge being chosen to match the type of computer. Seven- or nine-track tapes can be used. The new plotter is backed by the CalComp range of graphics software, which includes functional software for drafting, scientific work and business uses, contouring programs and a range of software for three-dimensional displays. (CalComp Ltd, A.M.P. House,

DeanwaH Road. Crovdon. .~urrev. Ene-

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COMPUTER AIDED DESIGN