A driving circuit controls a time for applying a drive signal to a piezoelectric element so as to bring a control in the number of ink droplets squirted from a liquid surface of liquid ink according to a gray scale level of an image to be printed on a printed object. According to application of the drive...http://www.google.de/patents/US5912679?utm_source=gb-gplus-sharePatent US5912679 - Ink-jet printer using RF tone burst drive signal
