Abstract: A method for determining the state of access control devices and sales or payment machines of an access control system by detecting sound profiles emitted during operation by a component or component group by at least one microphone. Based upon the recorded sound profile, an acoustic identification signature is created in a server or a central computer, which identification signature is based on the frequency spectrum of the recorded sound profile and/or the temporal change thereof. The acoustic identification signature is compared with a reference identification signature(s) stored in the server and assigned to a component or a component group. In the event of the detecting an acoustic identification signature which exceeds a predetermined first threshold value, increased wear of the component or the component group is detected, while if the deviation exceeds a second threshold value, a defect of the component or the component group is defected.

Abstract: A method for identification of vehicles (4) for operating a car park or a parking area is proposed in the course of which a vehicle (4) is identified at least by the sound profile emitted by the drive train of the vehicle which comprises a vehicle drive unit in the acoustic wave and/or ultrasonic range in at least one speed range.

Abstract: A method for determining the state of access control devices and sales or payment machines of an access control system by detecting sound profiles emitted during operation by a component or component group by at least one microphone. Based upon the recorded sound profile, an acoustic identification signature is created in a server or a central computer, which identification signature is based on the frequency spectrum of the recorded sound profile and/or the temporal change thereof. The acoustic identification signature is compared with a reference identification signature(s) stored in the server and assigned to a component or a component group. In the event of the detecting an acoustic identification signature which exceeds a predetermined first threshold value, increased wear of the component or the component group is detected, while if the deviation exceeds a second threshold value, a defect of the component or the component group is defected.

Abstract: A method for identification of vehicles (4) for operating a car park or a parking area is proposed in the course of which a vehicle (4) is identified at least by the sound profile emitted by the drive train of the vehicle which comprises a vehicle drive unit in the acoustic wave and/or ultrasonic range in at least one speed range.

Abstract: An apparatus is described for measuring the deposition of ice on the rotor blades (5) of a wind turbine (1), having a transmitting and receiving device with parts that are on the rotor blades (5) on the one hand and parts that are arranged in fixed positions and are connected to each other via a wireless transmission link on the other and having an evaluation circuit (9) connected to the transmitting and receiving device. In order to provide advantageous structural conditions, it is proposed that the transmitting and receiving device comprises passive transponders (6) on the rotor blades (5) and at least one stationary reader unit (7) for the transponders (6) and the evaluation circuit (9) has a comparator stage (10) for the minimum transmission output of the reader unit (7) required to read the transponders (6) reliably, with a programmable threshold value for this transmission output in the event of the deposition of ice.