This article discusses the CIELAB color spave within the limits of optimal colors including the complete volume of object colors. A graphical representation of this color space is composed of planes of constant lightness L * with an net of lines parallel to the a * and b * axes. This uniform net is projected onto a number of other color spaces (CIE XYZ, tristimulus RGB, predistorted RGB, and YCC color space) to demonstrate and study the structure of color differences in these spaces on the basis of CIELAB color difference formulas. Two formulas are considered: the CIE 1976 formula *** and the newer CiE 1994 formula ***. The various color spaces considered are uniformly quantized and the grid of quantized points is transformed into CIELAB colordinates to study the distribution of color differences due to basic quantization steps and to spacify the areas of the colors with the highest sensitivity to color discrimination. From a threshold value for the maximum color difference among neighboring quantized points searched for in each color space, concepts for the quantization of the color spaces are drived. The results are compared to quantization concepts based on average values of quantization errors published in previous work. In addition to color spaces bounded by the optimal colors, the studies are also applied to device-dependent color spaces limited by the range of a positive RGB cube or by the gamut of colors of practical print processes (thermal dye sublimation, chromalin, and match print). For all the color spaces, estimation of the number of distinguishable colors are given on the basis of a threshold value for the color difference perception of *** = 1 and *** = 1.

The state of the art in fully electronic space-division telephone exchanges shows that neither can semiconductor crosspoints directly replace reed relay contacts in Public exchanges, nor can hitherto semiconductor switching networks compete with reed relay switching networks. Though semiconductor crosspoints fulfill all transmission requirements, they are too expensive. Investigations on this field by the authors led to the following results. 1) A semiconductor crosspoint with high breakdown voltage and low on-resistance has been developed. This crosspoint can be connected to a subscriber's line and thus directly replace a reed relay in a public exchange at only slightly higher cost. 2) These crosspoints with high voltage capability can be combined with low cost, low breakdown voltage MOS semiconductor arrays in large-scale integration (LSI) techniques which are isolated from the subscriber lines by transformers to form a fully electronic switching network. 3) A crosspoint free of on-attenuation which can be monolithically integrated to crosspoint arrays has been developed; 4) A thick-film hybrid crosspoint for switching of commercial high-resolution video signals has been developed. The state of the art of optical switching systems shows that switching networks using a laser beam enable the transmission of wideband video signals with comparatively high crosstalk attenuation.