Abstract: A coil (6) forming part of a tuned circuit (8) is wound around a gapped magnetic core (2). As a magnetic stripe (14) is passed under core (2), variations to the amplitude and frequency of the circuit (8) occur dependent upon the magnetic data on the strip (14). Selected data are manipulated to derive several values (32, 36, 38, and 40) for combination via AND-gate (47). Only if the combination value is above a threshold value is an indication given that the stripe (14) is genuine and not an attempted copy.

Abstract: In a liquid crystal display, each pixel is formed of four separately energizable areas which have relative light outputs in the ratio 1:2:4:8 respectively, thereby allowing a range of 16 grey levels to be achieved by appropriate selection of areas. Each of the areas has a number of segments, which are spaced-apart but concentrically arranged, in order to have the same average position, so that different bit patterns cause the pixel to change brightness only, without any apparent positional change.

Abstract: A display device is formed by a matrix of surface-stabilized bi-stable ferroelectric liquid crystal elements each being separately settable by a matrix driver. To provide brightness control or color in the display, all the elements of the matrix are set in accordance with a portion of a signal for display and the amount of light passing through the matrix for that setting is controlled in accordance with the binary significance of the respective portion of the signal. This control is produced by varying one of the activation duration or intensity of a light source, such as sets of fluorescent tubes in accordance with the binary significance of the brightness information in the input signal. Half of the frame time (T) is used for the numerous setting operations on the matrix of elements and half is used for the backlighting operations of the various settings.

Abstract: A liquid crystal display has a matrix of pixels each with a continuously clocked counter used both as the data store and as the mechanism of grey scale generation. The grey level of each pixel is stored as the phase of the counter with respect to a reference count.The data bus, load clock, counter clock and master phase reference are all lines which transport signals common to a large number of pixels.The shift data line is used to propagate a bit which enables the counter load input. Each pixel circuit instructs the adjacent circuit that it is next to be loaded, by use of a clock delay. Thus pixels are loaded in sequence from data on the load bus, that data being between load clock pulses. The bistable circuit element, set from the master timing and reset from the counter, has an output which directly drives a bistable liquid crystal display device.

Abstract: A computer generally includes a program storage device for storage in memory of program or other information. The software or program may be expensive to produce yet can be copied without undue difficulty from the storage device.This invention provides a program storage device which does not output an address, as part of an instruction, if it is an address within the device. The data output from a programmable read only memory (PROM) is output to a data modifier where in response to a controller it is changed to a dummy address for output. Information to reconstitute the address is held in a stack then when the dummy address returns the controller causes an offset adder to return the original address. Steps can be taken to deal appropriately with conditional instructions and relative instructions.

Abstract: For ultrasonic or other mapping systems which use PPI scan, it is desirable to convert the data to a raster scan format for, say, T.V. display. This may be achieved by conversion in a frame store. It is here proposed to time the PPI scan so that points interrogated by the effective receiving beam lie also on line of a cartesian matrix in the mapped region which correspond to the raster lines of the display thus the conversion is directly achieved.