side along the knives 14 it will be appreciated therefore that the heald hooks 16 are arranged in an orthogonal grid pattern composed of rows 15 and rows 18 each heald hook 16 being located at the intersection of each row 15 and row 18 in accordance with the present invention there is provided a diagnostic system which includes a visual sensing means 30 and an electronic control 40 the visual sensing means 30 is preferably in the form of a video camera 31 which is mounted above and to one side of the top of the jacquard machine 10 so as to view hooks 16 as they rise to their upper shed position the image viewed by the camera is schematically shown in fig2 the electronic control 40 preferably comprise a computer which receives the video image from the camera preferably via a digitizer interface the computer is arranged to receive an operating signal o during each weaving cycle the operating signal o may be generated by for example a sensor on the drive shaft 42 of the jacquard in the case of a jacquard having mechanically operated pattern selection or may be generated from the electronic control of a jacquard having electronically controlled pattern selection on receipt of signal o the computer is arranged to grab an image from the camera and use the image to identify the presence of hooks located at their upper shed position and then determine whether or not all selected hooks have been raised preferably the camera is a monochrome camera and preferably the upper portion 16a of the hooks 16 have been.