A camera pod for an aircraft includes a housing with a plurality of camera compartments configured to downwardly angle a camera therein and a port for the lens of a camera. The container is provided with a hinge, an air-tight seal or gasket and a button-snap closure, and is decorative and aesthetically pleasing. The video content of a signal can be represented by a set of signatures that are generated for multiple series of frames within the signal. As a result, it is possible to provide stable image quality free from degradation of toner charge performance and toner supply performance even for long-term use. For changing the circuit constant, the variable capacitor is varied so that a resonance point becomes greater than an optimum resonance point most attenuating a high frequency in the second high-frequency power supply.