The invention relates to a system for determining whether the interior of a vehicle is occupied. The throttle valve is pivotable about a pivot axis in the pipe between the closed position and the open position and the restoring spring is supported on the valve end on a lever fixedly connected to the throttle valve and is supported at the pipe end on a bearing for accommodating a shaft extending coaxially with the pivot axis. The signal light pulse inputted is multiplexed by a multiplexer with the control light pulse optically delayed by an optical delay element so that the timing is matched with the signal light pulse, and introduced into an optical Kerr medium. Additionally, a first cross support can span the framework and a plurality of second electronic components can engage the first cross support. A collection of price rules is generated including, for each soft rule in the set of price rules, hard price rules that are associated with the product and that have the same price rule type as the soft price rule. The function element may be altered according to different needs; however, other elements need not to be altered, thus the whole structure thereof is simple.