Abstract: A method for authentication of sensor data (D) which is interchanged between at least one sensor (S1 to S4) and an associated receiver (2), in which a request (challenge) is first of all transmitted by the receiver (2) to the at least one sensor (S1 to S4) with an encrypted random number, this request is decrypted by the at least one sensor (S1 to S4), the random number is modified and the modified random number is used as a session key for the subsequent sensor data transmission (response). A first hash value (H) is calculated from the sensor data (D) at the sensor end; a cryptographic checksum (DS) is produced for authentication of the sensor data (D) to be transmitted, a second hash value (H?) is calculated from the first hash value (H) and the session key as a data block and is encrypted using the secret sensor key (GS), the authenticated sensor data (DS+D) is transmitted to the receiver (2), and the authenticity of the cryptographic checksum (DS) is checked at the receiver end.

Abstract: A mixer for mortar has part of its water feed introduced between a rotating isk and the floor of the disk housing, this water being propelled outward through an annular constriction in the clearance between the disk and the housing so that the rotor is kept constantly pressured by the inflowing water. The rest of the water is introduced through inlets spaced in a ringlike arrangement in the housing cover so as to produce a continuous water film on the rotating disk, onto which the powdered plaster and any other additives are fed.

Abstract: A method of and apparatus for producing gypsum fiber boards includes introducing shaped boards provided of a mash of calcium sulphate dihydrate and fibrous material and possibly additives after dewatering and shaping the mash into at least one pressure vessel and to heat the boards at saturated steam atmosphere to 120.degree.-160.degree. C. over a predetermined period. Thereafter, the boards are allowed to cool down within the pressure vessel to a temperature of about 100.degree. or less before being discharged therefrom.

Abstract: To control the earphone and microphone amplifiers as well as the balancing network of a subscriber's telephone terminal which is fed, through a subscriber line in communication systems, to the effect that the attenuations in subscriber lines of unequal lengths do not affect the transmission characteristics between the exchange and the subscriber, a circuit arrangement is provided for producing the necessary control function, which is simple, integratable and has minimum tolerances. Above a predetermined threshold value, a voltage proportional to the line current variations controls the emitter-to-base junction of two grounded-base transistors at the collectors of which the control current is available. The control currents produce their effect on the negative feedback of the microphone and the earphone amplifiers. An increasing line current causes the cotrol current to decrease, thereby effecting a stronger feedback and a reduced amplification.

Abstract: Wet plasterboard to be dried is advanced along a path. At an upstream portion of the path, air is heated and directed towards the plasterboard for initial drying of the latter. A portion of the heated air is withdrawn and passed through one section of a heat exchanger whose other section contains water which exchanges heat with the heated air. The heated water is passed through a section of another heat exchanger whose other section contains fresh air which is heated by the heated water. The heated fresh air is directed towards the articles for further drying of the latter at a downstream portion of the path. A portion of the heated fresh air is exhausted and recirculated at the downstream path portion.