A vector magnetic ink jet printer is arranged so that the ink droplets in the initial jet stream are alternately selected (i.e., magnetized) and unselected (unmagnetized). The interposition of unselected droplets between selected droplets prevents undesired magnetic interactions between selected droplets...http://www.google.de/patents/US4068240?utm_source=gb-gplus-sharePatent US4068240 - Vector magnetic ink jet printer with stabilized jet stream
