Abstract: A regulated power supply unit with an electronic transformer having an input for a transformer power supply voltage on the primary side, an output for an operating a.c. voltage with a higher-frequency component on the secondary side, and a control device with a variable resistor by means of which the operating a.c. voltage may be set. There is an inductive or capacitive separator component by means of which the higher-frequency component of the operating a.c. voltage can be separated out and taken as the input voltage to a first and a second rectifier circuit. The output voltage of the first rectifier circuit is applied to an amplifier-comparator circuit as its supply voltage. A reference generator circuit is connected to the first rectifier circuit and to the amplifier-comparator circuit. A reference for the operating a.c. voltage can be set by the reference generator circuit.

Abstract: Method and apparatus for detecting the distance between an ultrasonic objective and an object to be imaged in order to prevent contact between the two. For this purpose, light rays, after entering into an immersion means (water) between the objective and the object, being reflected by the object, and emanating from the immersion means are fed through the ultrasonic objective to a photo-receiver and converted into electric signals. The front face of the lens body of the ultrasonic objective is provided with an opaque ring zone. This arrangement makes it possible simultaneously to illuminate the object.