In the zoom lens apparatus, a lens frame for a variable-magnification lens or a correcting lens is configured of an inner frame and an outer frame, and any focus blurring due to variations in wavelength of subject light can be compensated for accurately by shifting the inner frame holding the lens relative to the outer frame. The disclosed invention is capable of racking a wide variety of configurations with different multiples of billiard balls. When so provided, the lighting apparatus may help provide a level of protection to objects andor surfaces that are subject to bumping, sliding or other abuse. The first packet of the transport packet carries only the navigation information including program clock reference information and does not carry presentation data. The resulting display allows for simultaneous monitoring and management of real-time process control and network information. An output by the model checker may facilitate identifying bugs andor livelocks, or authenticate a program as operating correctly.