Abstract: Traditionally, the parameters evaluation and characterization of amplitude modulation(AM), frequency modulation(FM) and phase modulation(.phi.M) signals are achieved utilizing analog test and measurement instruments. The advancement of high speed analog to digital converters and digital signal processing techniques have made this digital AM/FM/.phi.M demodulator an accurate, repeatable and cost effective alternative for the test and measurement of various modulation waveforms. This invention illustrates the design of the digital AM/FM/.phi.M demodulator.

Abstract: Printed Circuit Board Testing Apparatus is disclosed which utilizes a "bed of nails" of contacts with conductive probes mounted in an insulating plate on a grid of 0.050 inch spacing to make a plurality of electrical contacts with a printed circuit board under test. This large number of contacts are all connected to the edge of a plurality of printed circuit boards mounted perpendicular to the back of the plate. Paths on each of these printed circuit boards electrically connect the probes of the contacts to a large scale integrated circuit chip on which are a plurality of analog switches each controlled by one bit of a binary word stored in a multi-stage shift register also on the chip. One side of each switch is connected to a probe while the other side of the switches are tied together in busses to create a multiplexing arrangement to thereby connect ones of the large number of probes to a relatively small number of input/output leads also connected to the printed circuit boards.