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The HP 7470 was a small low-cost desktop pen plotter introduced by Hewlett Packard's San Diego division. It used a revolutionary "grit wheel" design which moved the paper held in place by a wheel with embedded grit and a pinch roller. The HP 7470 had only two pens, one on either side. It was much less expensive than the previous flatbed design. It was very heavy but had 4 pens. The HP 7475 used a rotating carousel with six pens. That plotter was used in greeting card kiosks. This design was also scaled up for very large pen plotters. These were driven by the HP-GL plotter language which used ASCII commands such as PA 300, 4500;PD;
Pen plotters became obsolete with the adoption of ink-jet printers, and processors fast enough to rasterize complex images. Houston Instrument and other manufacturers would follow with similar plotters.