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O Ohms: is a unit for measuring resistance or impedance of any electrical device. Omni directional transmitter: is a transmitter which sends the signal in all directions. Optical Filter: is a type of filter used in optics which selectively allows light of different frequencies to pass through. Oscilloscope: is a device which visually displays the wave form of any electrical signal on a screen. In CCTV, it is used trouble shooting and making adjustments of various components.