A method generates mechanical energy by storing water in a fuel-cell and a pressure equalization device. The drive also includes a first sensor and a second sensor. A linking mechanism connects the first and second lap belt retractors and is adapted to transfer motion between the first and second lap belt retractors. The first conductive path may further provide a sensed signal representative of state of the associated switch to break before make control circuitry to assist in minimizing a break before make delay time interval. Vapor generation can here be controlled on the basis of the vapor pressure in the evaporation region, wherein advantageously during operation of a soldering system the pressure in the corresponding process chamber can also be used for control in such a manner that there is always a pressure gradient and additional conveying means, such as pumps for the vapor supply, can thereby be avoided.