Abstract: A document verification scheme embeds in or deposits on a substrate/document a random distribution of dielectric particles that effectively create a unique electronically detectable signature. The dielectric constant of the particles is sufficiently larger than that of the substrate/document, so as to exhibit molecular level electric dipole moments, which cause a detectable modification of an external electric field passing through the substrate. Electronic signature verification is effected by comparing the digitized output of an electric field modification sensor with a digital code that has been stored previously in the data base. As long as the substrate containing the dielectric particle signature has not been altered, its randomly distributed capacitance characteristic will remain unchanged, and the two digital signatures seen by the comparator will effectively match one another, verifying authentication of the substrate.

Abstract: In a digital data recovery receiver, an optimal (in the Maximum likelihood sense) estimate of Es/No (dB) is obtained by the following mechanism. First, over a prescribed symbol span of N symbols, for each of 2.sup.B-1 -1 quantization bins, respectively associated with 2.sup.B-1 threshold levels used by a B-bit resolution analog-to-digital converter to digitize a received signal, the number of times that the received signal is quantized with respect to that level is counted. Each count total is divided by the number N of symbols in the span, to obtain plural ratios, respectively representative of probalities of symbol pseudo error rate over the symbol span. Using these ratios, respective Es/No (dB) values are derived from stored pseudo error relationships, each of which is associated with a respective one of the 2.sup.B-1 -1 quantization bins and defines the probability of symbol error rate in terms of Es/No (dB).