In a zoom lens infrom which a magnification changing optical unit for changing an overall focal length of the zoom lens can be insertedremoved, wherein a wobbling unit which can be slightly amplitude-driven in an optical axis direction to detect a best imaging position is placed closer to an image side than an insertion position of said magnification changing optical unit. In one aspect, the techniques include receiving sensor data values emitted by a sensor device, identifying the occurrence of a business event based on the sensor data values, and notifying an enterprise application of the occurrence of the business event. If the releasing jig is rotated so as to be pried, the retainer is pushed back diagonally downward along a guide groove and reaches a temporary retaining position. If necessary, the signal transmitted by at least one of the synchronized transmitters may be delayed, such that identical digital signals received from at least two of the transmitters by receivers in the region will arrive at each receiver within a prescribed time window.