Gray scale electrostatic recording system and a stylus driver therefor

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. When the transistor is cut off the inductive tank circuit, including said inductor, produces a high voltage output pulse proportional to the original signal placed on the transistor base. The width of said output pulse is related to the value of the resistor in the inductive tank circuit which also controls the damping of the output pulse.