The most flexible arrangement of jet.engine technology is where the print engine electronics reside in a stainless steel box, which is the controller, driving 1 to 4 pens or cartridges in any configuration, as desired. For example, 4 cartridges can be made into two 25 mm (1") printers or four 12.7 mm (1/2") printers. Or one or more printheads may have different colours printing highlighted text.