Abstract: A tensioning system for a fuel cell stack includes a pressure plate with a contact surface for bearing against the fuel cell stack, a tensioning element which is arranged on a side of the pressure plate which is opposed to the contact surface, at least one spring element which is arranged between the pressure plate and the tensioning element and has a spring axis, along which the at least one spring element can be tightened, and at least one tensioning device. The tensioning device is designed to exert a pressure force on the tensioning element. The pressure force is directed along the spring axis and in the direction of the pressure plate. The tensioning element is configured to transmit the pressure force with pre-tightening of the at least one spring element to the pressure plate.

Abstract: There is disclosed a safety switch for generating an enable signal as a function of the position of a moveable guard door. The safety switch comprises a door part and a frame part. The door part has an activator, which can be displaced between a first and a second position. The frame part has a cutout, in which the activator can engage in the second position. A locking element is arranged on the door part in order to lock the activator in the second position. A sensor is designed to detect at least one of the positions of the activator in order to generate the enable signal as a function thereof.

Abstract: There is disclosed a safety switch for generating an enable signal as a function of the position of a moveable guard door. The safety switch comprises a door part and a frame part. The door part has an activator, which can be displaced between a first and a second position. The frame part has a cutout, in which the activator can engage in the second position. A locking element is arranged on the door part in order to lock the activator in the second position. A sensor is designed to detect at least one of the positions of the activator in order to generate the enable signal as a function thereof.

Abstract: A gamma radiation detector comprises a semiconductor body and two metal electrodes attached to two spaced surface zones of said semiconductor body, said detector being characterized by the combination of the following features: (a) The semiconductor body consists of a uniform semiconductor material of the same conductivity type; (b) Charge carriers of both types are mobile in the semiconductor material and the product of their mobility multipled by their free drift time (life) exceeds 10.sup..sup.-9 m.sup.2 V.sup..sup.-1 for each type of carrier; (c) An insulating layer which is thin in relation to the distance separating said two surface zones is interposed between at least one of said electrodes and the surface zone to which it is attached.