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hi
when i was in college in 1980 i used an HP9825A desktop calculator in a physics lab. Connected to this thru what i think was the hp-ib bus(that was new at the time, i think)was a real nifty printer/plotter. I cannot find the model number of this thing anywhere. It is not the 9862A. the plotter that i remember did not use any multi-pen setup. it used a cool printing head that looked like a little hand that moved to white letters like a human hand would spell them out - it didnt stamp them like a typewriter. I appreciate any and all help in this matter.

You're probably talking about the 7470A. This plotter came with one of three interface options: Option 001 was RS232, Option 002 was HP-IB, and Option 003 was HP-IL. (I have one with the HP-IL interface.) It uses 2 pens, which are mounted under the front cover, one on the left and the other on the right. The pen holder has a couple of little "fingers" to hold the pens. When plotting the pen holder slides over to one side or the other, grabs a pen, and moves from side to side while the paper moves backward and forward. The combination of movements allows any shape to be plotted. If two colors are being used the plotter draws all of one color's lines first. Then it puts the first pen back, goes to the other side and grabs the other pen, and draws the rest of the lines. It's pretty fascinating to watch.