Talk:HP 7470

Pen Plotters Had Physical Controls; Could Pause & Switch Pens
HP Pen Plotters also had physical controls (buttons). So, for example, you could pause the action, press a button for the 7470 to grab the other pen and switch physical pens. Thus even this two-pen plotter could use more than two colors "at once". Of course you had to be quick to pause the action at the right time to do your pen swapping. Also, continuing the action with no pen in place was also possible. Why would you do that?. One example is to overlay plots (say from an oscilloscope that had HPGL output [such as the Leader 3100A oscilloscope I have {vintage 1993}]). You could plot two waveforms atop one another, but no need to redraw the axes etc. So for a totally separate plot output from the oscilloscope, you could begin with pausing as soon as it uptakes the pen; then hit pause; take away the pen; resume as it redraws the axes etc with no pen (though it would be literally going thru the motions); pause again and put a pen in with the color of your other waveform to plot atop the original. The oscilloscope had capabilities for reference waveform and so on, but this is just an example to say that you could watch and interact with the HPGL Pen Plotters using their buttons, besides using software or other means of giving them HPGL commands via the GPIB (HPIB)(IEEE-488) interface.166.123.216.29 (talk) 22:25, 14 August 2013 (UTC)