Abstract: Methods and apparatus for performing Brinell hardness test measurements produce hardness numbers and average Brinell indentation diameter readings automatically and minimize operator intervention and hence, operator error. The apparatus uses a light source, a video camera, a video image digitizer and a computer having a display device. In the method of the invention, electromagnetic radiation is applied to the indentation at an acute angle to the surface of the test specimen in which the indentation has been made. The electromagnetic radiation reflected from the indentation and the surrounding area is sensed. Differences in intensity, such as between light and dark, are digitized and the resulting digital field is numerically analyzed to produce a diameter, preferably major and minor diameters, of the Brinell hardness impression. The diameter or major and minor diameters are used to compute a Brinell hardness number which is displayed by the computer.

Abstract: The present invention provides a two-way sound transducer system, including amplification circuitry within an ear-muff type attenuator, to enable the user to listen to principally voice communications (although other forms of sound can be transmitted) from a remote location and in response thereto answer a communication by talking in a natural voice, irrespective of the total surrounding noise present at the location of the user.