In a matrix array for the supply of an electrographic stylus writing apparatus, a plurality of styli are driven by short pulses through R/C networks. The styli are divided into subgroups and parallel capacitors connect the styli of each subgroup to a high voltage switch which is responsive to a capacitor...http://www.google.de/patents/US4353080?utm_source=gb-gplus-sharePatent US4353080 - Control system for electrographic stylus writing apparatus
