Abstract: A conductivity measuring device comprises a low-potential intermediate electrode which is capable of being in connected state by a switch and which is disposed between a couple of measuring electrodes for transmitting and receiving. Each of said electrodes is made contact with a body to be tested so that the conductivities of the surface and the inner portion of said body to be tested can be measured, respectively.

Abstract: An apparatus for transmitting electric power and information signals between a rotating element provided at a rotating shaft and a fixed element provided at the circumference of the rotating shaft. Both the rotating element and fixed element are configured as coils, and they perform transmission by an electromagnetic induction. Each coil is formed in a cylindrical form, and has a split structure comprising plural blocks which can be mounted on the shaft from the circumference of the rotating shaft. The rotating element and fixed element are mounted respectively on a rotating shaft of a machine and a fixed side of the machine, and electric power and information signals needed by the rotating element are transmitted from the fixed element.

Abstract: A device adapted to transmit a signal and a power with an electromagnetic wave or light being as the transmission medium. This device comprises active and passive modules each provided with means for effecting transmission and reception of at least one of the electromagnetic wave or light, and a signal processing circuit. Each module may further comprise an output or frequency control circuit. One of these modules is provided at a moving body such as a rotary body, and the other is provided at a fixed body to effect both signal transmission and power transmission between the moving and fixed sides.