Abstract: An oscillation circuit having multiple separately addressable oscillator stages for applying RF voltage across selected capacitive loads where each stage includes a power driver, a transformer and a quench/clamp circuit. The oscillation circuit includes one enablement circuit responsive to an externally applied enablement signal and address signal and a common feedback circuit connected between one end of all of the transformers and the enablement circuit. An externally applied address signal and an enable signal selects a particular oscillator stage and initiates action of a power/driver circuit to provide an initial pulse of AC current through the associated transformer for a preset period and the feedback circuit detects negative zero crossovers of the waveform of current through that transformer primary to maintain actuation of the driver circuit for as long as the external enable signal is present.

Abstract: A printer autocontrast system measures the current passing from a toner reservoir to a charged dielectric member which receives toner from the reservoir. The charge delivered to the drum in this way is scaled and compared to an estimate of the intended image charge to develop an error signal. The error signal corrects a control parameter to adjust the operation of an electrographic printhead which forms a latent image on the dielectric member.