Abstract: An electrostatic gray scale printing system is disclosed having particular utility for producing gray scale images from signals received from a suitable data source such as a computer, telecommunications line, data storage device or the like. A unique, high voltage, pulse generating circuit is provided for producing gray scale voltage pulses between 300 and 600 volts to the individual styli making up said printing device. The circuit utilizes a conventional, low voltage, power supply and a low voltage gray scale intensity signal input to produce the required high voltage printing pulses. The circuit, per se, consists of a high voltage transistor having a relatively large inductance connected in its emitter-collector circuit path. Current flows in the transistor in response to an input voltage applied to the base of the transistor. The collector current is proportional to the value of the input signal divided by the emitter resistor.

Abstract: An ink jet printing head comprising a head body made from a material having high specific stiffness and the head body includes an ink passage which is kept small to retain the high body stiffness. The ink passage comprises a narrow slot connected with internal holes in the body which lead to ink inlet and exit ports. A nozzle plate having a plurality of orifices is fixed to the front of the head body and a piezoelectric crystal is fixed to the back of the head body. The piezoelectric crystal is kept thin compared to the head thickness, typically on the order of 1/20 to 1/30 of the body thickness, so that the effect of the crystal on the resonant characteristics of the assembly is kept small. The ink jet head provides a plurality of columns or jets of ink which are excited in such a way as to break up into uniformly and equally spaced drops at a fixed distance from the nozzle plate containing the orifices which produce the jets.