Abstract: The electrically controlled force transmitting apparatus includes a drive member having an electrically conductive surface and a driven member having an electrically conductive surface, which are arranged to be opposed to each other with a small space therebetween, a fibrous member provided in the space between the opposed electrically conductive surfaces of the drive and driven members, and a voltage supply source connected across the electrically conductive surfaces, whereby by applying a voltage across the opposed surfaces, there is induced a shear stress and a force is transmitted from the drive member to the driven member. The space in which the fibrous member is arranged is preferably filled with an electrically insulating fluid medium.

Abstract: A method for measuring a propagation speed of ultrasonic wave transmission through a medium of known dimension, comprises a step of generating a plurality of pulse trains at each cycle of a predetermined time interval t.sub.i, each of the RF pulse trains being composed of at least two consecutive RF pulses generated at a predetermined time period t.sub.s for exciting an output ultrasonic wave. The measuring method also includes the step of inputting a signal indicative of a superposed ultrasonic echo occurring due to the output ultrasonic wave applied to the medium, on a Y-axis of an oscilloscope, and inputting continuous X-axis trigger pulses having a predetermined period t.sub.o on an X-axis of the oscilloscope. The speed of the ultrasonic wave is derived on the basis of a length of the medium and the period t.sub.s read through the oscilloscope when an amplitude of the echo signal becomes greatest and the echo signals are overlapped in phase, by adjusting a value of the period t.sub.