Abstract: A method and a device are provided for determining the moment that a layer of tacky material needs to be rejuvenated. Typically, the layer is present on a cleaning member for removing contaminants such as paper dust and softened toner material from a fusing surface. The method includes measuring the light reflection value of the layer of tacky material, comparing the measured light reflection value with a reference value and rejuvenating the layer of tacky material as soon as the measured light reflection value differs by a predetermined value from the reference value. The device implements the method of the present invention.

Abstract: An amplifier comprising a first and a second amplifier element, whose outputs are connected to a load, a difference circuit which comprises a comparator, in which the output signal of the first amplifier element is compated with the input signal thereof to produce a correction signal which is applied to second amplifier element, and a second substantially identical difference circuit which comprises a comparator in which the output signal of the second amplifier element is compared with the input signal thereof to produce a correction signal which is applied to the first amplifier element; a desired signal to be amplified being applied to both amplifier elements. The two amplifier elements, which may be preceded by preamplifiers, take the form of power amplifiers. Because the distortion signals appear at the load as "common mode" signals, the overall distortion becomes substantially zero in the case of equal attentuation in the two difference circuits.