Abstract: An ultrasonic sensor for non-invasive detection of air bubbles in a liquid flowing through a tube comprises two half-housings capable of being assembled together and two mutually opposed ultrasonic transducers, one installed in each of the half-housings. For acoustic coupling of the tube to the two mutually opposed ultrasonic transducers, each half-housing contains a chamber closed off by a flexible membrane and filled with a fluid highly transmissive of sound. The fluid displaced by the tube inserted between the two half-housings forces the membrane up in the form of a bulge on either side of the tube. In this way, an excellent contact is obtained between the chamber filled with sound-transmissive fluid and the tube. The membrane may be embedded into the side walls of the half-housings and cylindrically arched along the same.

Abstract: A motion picture camera has a rotary shutter driven by a DC motor which is supplied from a battery. The camera also has an arrangement for making light markings for identification purposes on the film in the camera. This arrangement includes a light-emitting diode and a capacitor which is charged by the battery and discharges across the diode. The electrical circuitry is such that the capacitor is connected to the battery only when the motor is disconnected therefrom; inversely, when the motor is to be connected to the battery in order to operate the shutter (and also to advance the film), the capacitor is first disconnected from the battery before the motor is connected to it and then discharges across the diode. The circuit also suppresses afterglowing of the diode.

Abstract: The reproducing apparatus, such as a motion-picture film projector, stops recording medium transport in response to interrupt-transport frame markings on the recording medium and reproduces the thusly marked image frames as still images. Interrupt-transport frame markings are provided at the terminal frame of each motion-picture scene on the recording medium, or at each still-shot image frame on the recording medium, or both. The user of the reproducing apparatus can select automatic reproduction of motion-picture scenes interspersed with automatic still reproduction of still shots, and can additionally select automatic still reproduction of the terminal frame of each motion-picture scene.

Abstract: The user of a motion-picture camera selects between motion-picture and single-exposure operation, and presses a release member to initiate shooting, letting go of it to terminate motion-picture shooting. Each time the user lets go of the release member, an internal device provides an interrupt-transport marking alongside the just exposed film frame, or phase shifted relative thereto. Alternatively, the interrupt-transport marking is provided the next time the user presses the release member. In this way, the terminal frame of each motion-picture scene, and each and every one of the interspersed single-exposure shots, is provided with an interrupt-transport frame marking. Thus, if the film is run through a reproducing apparatus provided with a marking detector, detection of each interrupt-transport marking during motion-picture reproduction causes the terminal frame of each motion-picture scene, and also each one of the still shots, to be persistently reproduced as a still image.