Abstract: A number of consecutive samples in unit distance code (here Gray code) are effectively stacked and supplied to respective sum and threshold devices 20 corresponding to each bit position, to determine the bulk property or “generic result” of the consecutive samples. This filtered output is converted back to binary and analogue if required. The digital filter may be used in any of the above applications to “clean” data.

Abstract: The comparators described herein comprise bit manipulation cells of a number of logic cells each built up of AND, OR etc. logic gates interconnected in parallel to make up one or more layers and do not rely on clocks, instead operating asynchronously. This makes the comparators highly robust and fault tolerant, and well suited for use as binary neurons in high integrity systems. They are less susceptible to radio frequency interference induced data corruption than alternative register-based implementations. Planar Hamming comparators capable of comparing two dimensional input arrays are also described.

Abstract: A novel architecture is described for applying a sum and threshold function to a weightless input string and a weightless threshold string. The sum and threshold function is carried out by distributing the input bits in random manner (12) between a number of sum and threshold devices (14), whose outputs are supplied to a second layer of one or more sum and threshold devices (16).

Abstract: A thermometer code converter for converting weightless binary tuples of 2 or higher dimensional arrays into a thermometer or aggregate code comprises a series of layers (16, 18) each made up of bit manipulation cells (10) which collectively cause set bits to be shifted towards a required bit position. The bit manipulation cells are made up of logic elements (12, 14) and the entire converter may be asynchronous. Also disclosed is a sum and threshold device which employs a thermometer code converter and a bit selector device.