An optoelectronic sensor for safeguarding a hazardous area, such as a light grid, has a first and a second sensor part. The transmission unit has a rotatable forward-reverse tension cam and a tension cam. A fixed and accurate fit of the tool module on each bar is ensured by means of this groove. A voltage is applied between the first and second interconnections to measure a relative positional offset amount between the via-plug and the second interconnection. The linkage device interconnects the operating unit and the leg rest frame, and is responsive to operation of the operating unit for moving the leg rest frame between the folded and unfolded positions.