Abstract: An adaptive system for binary data compression incorporating a coding scheme which is simple to implement, which limits codeword length and which can be implemented by software. Data compression is achieved by assigning four bit codes to the eight most frequently occurring characters in the data and eight or nine bit codes to the remaining characters wherein the code assignment is made according to a continuously updated evaluation of character frequency distribution. Run length encoding may be used in conjunction with this technique, to achieve further data compression. For transmission, error control protocols are applied to the compressed data where such protocols may include the use of forward error correcting (FEC) coding and an automatic repeat request (ARQ) system. The data may be transmitted using a burst error control system based on interleaving so that a single error correcting FEC coding can corrects bursts of errors characteristic of a telephone system.

Abstract: Textile articles are inspected for size, defects by forming an image e.g. in a video camera, capturing data representing at least salient features of the image, comparing the data automatically with reference data, and effecting a selection process in accordance with the result of the comparison. Articles e.g. socks, presented as a succession of imperfectly matched items, can be sorted for size e.g. into categories of leg and foot length.

Abstract: The condition of an article e.g. a multihead tool array is compared after having been subjected to some operation with its previous condition e.g. before and after a drilling or other operation of the tool array by forming an image, e.g. a video image, of the article before the operation and automatically comparing it with a second such image formed after the operation. Known image enhancement techniques can be used, and statistical techniques used in data processing equipment to detect significant differences between the images.