Abstract: A coin validating system typically used in a coin operated machine electrically couples a stationary coin to the tuning coils of an oscillator circuit. While the coin is in a stationary position and the oscillator is tuned to a first rest frequency, the output frequency and output amplitude of the oscillator is measured. The metal coin will increase the signal frequency from its rest frequency and will decrease the signal amplitude from its rest amplitude. While the coin is stationary, frequency and amplitude are measured and compared with expected parameters of a valid coin. If a match is made, the rest frequency of the oscillator circuit is changed. At the second test frequency, signal frequency and amplitude are measured and compared with expected frequency and amplitude parameters for a valid coin. Only if a match is made at both the high frequency and the low frequency is an accept gate actuated.

Abstract: Proposed is a ceramic-made electrostatic chuck consisting of two insulating ceramic layers and a metallic electrode layer integrally sandwiched between the two insulating layers, which has a very quick response characteristic to turning-on and -off of the electric voltage applied to the electrodes without affecting the very high electrostatic attracting force. This improvement can be obtained by forming the insulating ceramic layers from a specific ceramic material consisting of a highly resistive ceramic material such as alumina and the like and titanium nitride admixed with the former in an amount not exceeding 5% by weight but sufficient to impart the insulating ceramic layers with a volume resistivity in the range from 1.times.10.sup.8 to 1.times.10.sup.13 ohm.cm at 20.degree. C.

Abstract: In an integral multilayer analytical element of a flat sheet type comprising a plurality of layers for quantitative analysis of an analyte in a liquid sample, the improvement which comprises at least two layers of a microporous sheet material arranged adjacent to each other, said at least two layers being combined by an adhesive provided in part on the interface of said layers, whereby the interface allows essentially uniform passage of a liquid therethrough.