An improved modulation structure for the marking head of an ionographic marking aparatus for increasing the effective lifetime of the modulation electrodes in the highly corrosive atmosphere of such a device. A relative bias on the order of about 10% of the ion output cut-off bias is imposed across the...http://www.google.de/patents/US4727388?utm_source=gb-gplus-sharePatent US4727388 - Marking array having improved corrosion resistance
