A safety vest unit is disclosed having at least one compactly packed safety vest and also having a packaging of a thin flexible fabric that encompasses the at least one safety vest. A sense amplifier detects voltages discharging through the high and low resistance elements to determine the resistance state of an element being read. At least one second, independent, also hydraulically pilot-controlled valve is designed such that this valve is activated in a specified range of the variable pilot control pressure. The fill tube passes through the first and second openings. Upon a physical connection of the required component with the installable device, the actuator retracts the plunger, thereby enabling the installation of the installable device. For improving safety particularly in the event of a rear impact, the foam material is constructed as an essentially nondeformable matrix.