Abstract: A invention relates to a transformer having a primary coil and a secondary coil, with a ferromagnetic core inserted in a coil former. The alternating current resistance of the primary coil (3) drops on reaching a triggering temperature (TC) which lies above the operating temperature but below the softening temperature (TW) of the coil former (6) and/or insulation of coil winding (3, 4). The coil core (5) may consist at least partially of a material with a magnetic permeability which drops when the triggering temperature (TC) is exceeded.

Abstract: A method is described to contactlessly measure the brake temperatures of passing railroad cars, whereby the temperatures of all current practical brake types, for instance shoe and disk brakes at the wheels, but also of separate brake disks, can be measured. The method is characterized by using a known measurement apparatus with optics followed by an infrared sensor, whereby the measurement axis of this apparatus scans the passing wheel at a height 1 to 5 cm above the rail surface, the measurement axis "looking" from the rear-bottom, namely at an anagle alpha to the horizontal of 10.degree. to 22.degree. and at an angle omega of 7.degree. to 18.degree. to a horizontal line which is perpendicular to the rails, on the wheel. The measurement apparatus is controlled by track switch means activating the apparatus as long as the wheel rolls through the measurement axis.

Abstract: The invention concerns a system to detect irregularities in the geometry of railway wheels. The system is characterized in that a linearly expanding accelerometer is solidly joined to the rail underneath its head. The accelerometer sensitivity is constant over its entire length and generates a voltage proportional to the acceleration of the rail. For different damages, the rail acceleration takes place in different directions, whereby the voltage amplitude, depending on the type of damage, evinces opposite polarities. Frequency filtering or frequency analysis permit the determination of further criteria which, together with other weighted criteria, are used to characterize wheel damage.

Abstract: Method for directly bonding copper foils having a copper oxide layer to oxide-ceramic substrates by heating the ceramic substrate covered with the copper foil in an oxygen-containing atmosphere to a temperature above the eutectic temperature of Cu and Cu.sub.2 O, but below the melting temperature of copper in a vacuum furnace at a pressure of not more than 1 mbar while maintaining a furnace atmosphere with a partial oxygen pressure between 0.001 and 0.1 mbar.