A plotter that uses an electrostatic method of printing.  Liquid toner models use a positively charged toner that is attracted to paper which is negatively charged by passing by a line of electrodes (tiny wires or nibs).  Models print in black and white or color, and some handle paper up to six feet wide.  Newer electrostatic plotters are really large-format laser printers and focus light onto a charged drum using lasers or LEDs.  See 
electrostatic.
Electrostatic Plotter
This early plotter from CalComp used a dry toner process like a laser printer.  LEDs beamed light onto a charged plate and produced monochrome drawings at 400 dpi.  (Image courtesy of CalComp, Inc.)