Abstract: Provided are an organic light-emitting compound represented by Formula 1 and an organic electroluminescent (EL) device using the same: The organic light-emitting compound has thermostability and photochemical stability in addition to superior electrical features. The organic EL device using the organic light-emitting compound has low driving voltage, high efficiency, and superior color purity.

Abstract: A charger for charging the surface of a photoconductive drum by a contact charging method in an electrophotographic image forming apparatus includes: a charge roller for charging an unexposed surface of the photoconductive drum to a prescribed potential by contact with the surface of the photoconductive drum; a power supply connected to the charge roller, for supplying a variable DC charge voltage to the charge roller; a potential sensor installed around the photoconductive drum, for detecting a charge potential value of the unexposed surface of the photoconductive drum; and a controller for comparing the charge potential value detected by the potential sensor with a specified value, and changing the charge voltage generated by the power supply upon detecting any difference therebetween, so as to maintain the charge potential of the photoconductive drum at a constant value.

Abstract: A video signal processing system has luminance signal and a chroma carrier modulated with chrominance information. The system includes circuitry responsive to the chroma carrier for generating a phase alternating carrier having a phase alternating from field to field; circuitry for modulating a selected luminance signal on the phase alternating carrier and circuitry for adding the modulated phase alternating carrier to the chroma carrier modulated with chroma information.