Abstract: An air filter cartridge is mounted in an air purification device of a commercial vehicle. The air filter cartridge includes an identification device, the information of which can be recorded by a recording device. The method detects the characteristics of an air filter cartridge for use with the air purification device.

Abstract: In a two-wire line between a transmitter and a receiver, voltage or current pulses are used to transmit information, the content of which is contained in the period duration. This is achieved in that a transmitter connects or disconnects the operating voltage for a receiver using a switch. It is not necessary to have a digital-analog conversion or the reverse. Furthermore, a high pulse-duty factor is used, so that the supplying of the receiver is always guaranteed.

Abstract: In a device for measuring the distance to an obstacle, a second transmission pulse as a control measurement for an ultrasonic distance measurement is transmitted only when an echo signal has been received for a first transmission pulse. In addition, a timing window, within which the expected echo signal falls when it is reflected by an obstacle, is created. In this manner, interference signals are advantageously suppressed and the measuring time is accelerated, so that for an application in a motor vehicle to measure distance, a current measured value is always known while the vehicle velocity and the path covered are taken into consideration.

Abstract: An auxiliary back-up and trailer coupling device for motor vehicles includes ultrasonic sensors mounted on the motor vehicle. The ultrasonic sensors transmit and receive sound waves, and are linked to a control and display device. The device permits the position of a trailer unit that is equipped with a coupling device and arranged behind the motor vehicle to be exactly determined. The trailer is equipped with a coupling device, preferably a tow bar, and has an additional transmitting and receiving ultrasonic sensor.