Abstract: Multistage digital signal multiplying and adding apparatus suitable for a multistage filter includes a plurality of addition stages each having adding devices for forming a succession of partial products together with selectors operable in a first condition to connect sum and carry outputs of the adding devices within a stage to further adding devices within the stage or a second condition to supply outputs to a further stage, the selectors being operable to change condition without resolving carry signals in one stage through all bit positions of that stage. The output of one stage is connected to a subsequent stage during a first cycle of product formation of the subsequent stage so that the output is accumulated with the first partial product of the subsequent stage.

Abstract: A multi-stage apparatus has an input which is coupled to an output by way of a plurality of first stages. The stages are sequentially coupled together to form a chain. A spare stage, which is substantially identical to at least a selected one of said first stages is also provided. The apparatus also includes programmable logic means arranged to uncouple said selected first stage from said chain and to couple said spare stage into said chain such that the input remains coupled to the output by the same number of stages. In this way a redundancy scheme for the multi-stage apparatus is implemented.

Abstract: A cascaded array of devices, each having electrical signal processing elements arranged to process simultaneously the same input data, is provided with inter-device connections including signal delay so that an intermediate result of processing by a second device is combined with an output which was derived from a first device at a time related to that at which input data was input to the second device for use in forming its intermediate result.

Abstract: Thermal-radiation imaging devices, elements and systems are described. The device comprises on a substrate (2) e.g. of sapphire semiconductor bodies or body portions in the form of parallel elongate strips (1), e.g. of cadmium mercury telluride. Biasing-electrode means (6 and 7) e.g. of gold are spaced on the strips (1) for causing a bias current predominantly of majority charge carriers to flow along each strip (1). The bias current supports an ambipolar drift of radiation-generated free minority carriers in the opposite direction. At the area of read-out means (8) in the drift path each strip (1) branches into two parts separated by a slot (13) parallel to the strip (1). One part (11 in FIG. 2) provides the continuation of the drift path, while a read-out connection comprises the other part (12 in FIG. 2) and is separated by the slot (13) from the adjacent biasing-electrode means (6 or 7).