Abstract: Speech synthesizing apparatus is provided using digital coded values specifying parameters of a sound to be reproduced. The apparatus has a voiced sound generator using digital values specified by input parameters to represent three formant waveforms respectively which are sampled at substantially constant intervals, the parameters each expressing in relation to the sampling interval the frequency of the formant concerned. At each sampling, the input parameters are arranged to derive for each formant waveform respectively a value representative of the instantaneous amplitude of that waveform in relation to the others, the three values obtained then being combined to produce a resultant value representing an instantaneous amplitude output of a voiced sound component waveform. This output waveform is subjected to modification by attenuation and the addition, if required, of an unvoiced sound component before being passed through an analogue converter to a sound reproducing transducer.

Abstract: A motor drive system for driving a motor according to a predetermined motor speed curve in which a predetermined count of pulses of constant time increment is utilized to produce an output signal characteristic of an increment of motor movement. In addition the control signal is used to control the time interval between successive occurrences of the output signal in accordance with the motor speed curve.

Abstract: A bearing assembly and drive shaft particularly useful in connection, for example with a point-of-sale terminal in which the drive shaft is held within the terminal by a simple bowed spring retainer which spring-loads the bearing body elements against the side walls of the print stations of the terminal and which is easily removable so that the bearing assemblies and shaft can be removed from, and inserted in, the terminal by a simple bayonet type action. This concept provides a drive shaft in a POS terminal which facilitates maintenance of the terminal in situ, if desired.

Abstract: A data processing system in which a sequence of records, each record containing data items of various types, is processed. The system is operable in a "remember" mode in which, if a data item of a particular type is not present in a particular record, the result of the last time that type of data item was processed is used as the result for the current record. This permits data files to be stored in a compressed form in which repeated data items are omitted.

Abstract: The printed circuit board testing apparatus includes resiliently loaded probe pins carried in a support so that the pins can individually move relative to the support. A sealing means is positioned between the support and the printed circuit board, and is effective in operation to form a closed boundary enclosing a space occupied by the probes and the circuit connections and to enable a pneumatic clamp seal to be produced between the sealing means and the circuit board, to hold the probe pins in contact with the circuitry of the board.

Abstract: In printing apparatus in which a line of characters is printed on a record medium, by means of differentially timed operation of a line of print hammers, as the characters pass predetermined columnar positions of the record medium, the character font size can be changed. On each change of front size, a control circuit adjusts the timing of the actuation of the hammers so that the number of printing cycles necessary to print a line of characters is varied according to the font size used.

Abstract: A closed-loop servo system in which the parameter to be controlled is caused to follow a predetermined profile by approaching the profile, if there is an error, at a rate independent of the magnitude of the error. The system repeatedly tests for an error and adjusts a control input by a predetermined step each time one is found. In a preferred implementation the velocity of a d.c. motor is controlled by means of an up/down counter the value of which controls the motor current.

Abstract: The present invention is concerned with multilayer printed circuit boards which have more than a single plane of interconnection conductors spaced away from a common plane, such as an earth or power plane. In such a case the conductors of the interconnection layers form transmission lines having respectively different impedances, depending on their distances from the common plane. The invention contemplates a pattern of conductive areas distributed over one of the surfaces of the multilayer board, the surface chosen lying on the opposite side of the planes of conductors from the common plane, the pattern configuration being chosen more nearly to equalize the impedances of the conductors. The areas of the pattern are preferably connected to the common plane.

Abstract: A data file searching system in which data is compared with a search key, and the results of the comparison are then analysed by a processing unit. The action of the processing unit is initiated by an end-of-record signal which is generated in accordance with an end-of-record criterion. This criterion can be varied, and this permits the boundaries between records to be effectively varied.

Abstract: An inverter switching circuit, for example for a power supply, including semiconductors in push-pull configuration. To compensate for differences (basically in storage time) between the semiconductors in the two limbs the input pulse to each limb is of a reference duration plus the difference between the output and input pulses of the other limb. In a modification the input pulse for each limb is of the reference duration less the difference between its own output and input pulses.

Abstract: A system for hard wiring information into large scale integrated circuit elements, in which a waveform generator produces a plurality of fixed patterns each representing a portion of the information it is required to hard-wire into a particular element. The wired-in information may be used in uniquely identifying the individual circuit elements. Each element has at least two terminals to which a portion of the information is applied by connecting the terminals to various combinations of lines of a group of distribution lines to which the waveforms are applied. The terminals of the circuit elements each receive a plurality of bits of the wired-in information.

Abstract: A code converter comprising a pair of memories which are addressed by respective halves of the input code. The outputs of the memories are concatenated to provide an address for a third memory. The output of the third memory provides the output code. The converter is initially set by applying the desired input codes in sequence, and writing the contents of a counter into the addressed locations of the three memories, the counter being incremented for each new input code. A particular example of the use of such a converter is for assigning replacement addresses in an auxiliary memory for faulty locations in a main memory.

Abstract: A data processing system is described in which a plurality of microprogram address registers are provided, some of the registers being associated with operations involving a processor and others of the registers being associated with peripheral devices. Each register corresponds to a different level of microprogram interrupt and the registers associated with processor operations correspond to levels lower than the levels associated with the peripheral devices.

Abstract: An array processor, operative as the peripheral of a sequential machine. Each processing element is organized on a bit-serial basis, with single-bit registers and a bit-addressable store, and the array is controlled by a microprogrammed main control unit. These features result in an extremely flexible arrangement.

Abstract: An information retrieval system in which each record in a file is scanned and a hit signal is produced if it matches a search criterion. The hits are stored in a plurality of bit maps. Each record has an identifying index, which is transformed in a number of different ways to produce addresses for the bit maps. The outputs of the bit maps are combined to produce a stored hit signal. The number of hits is compared with the number of stored hits to determine whether any spurious stored hits have been recorded and, if so, the transformations are modified.

Abstract: A stage of a pipeline data processor has a store associated with it, and when that stage requires to write data into a specified address within that store, but the data to be written is not yet available, an indication of the address is stored in a special reserved register, so as to permit subsequent accesses to the store without waiting for that data to become available. When the data eventually becomes available, it is written into the store, using the contents of the register for addressing the store. This prevents hold-ups in the pipeline and hence increases the effective rate of instruction execution.

Abstract: Instructions are written in multi-word blocks into an instruction buffer from a slave store, and then scanned sequentially. The instruction buffer is unequally divided, a first part of a block being written into the smaller portion of the buffer during scanning of the larger portion, and the remainder of the block being written into the larger portion during scanning of the smaller portion. Thus, more time is available for an initial write from a block, which is when delays are more likely to occur due to the block having to be fetched from main store.

Abstract: A multi layer printed circuit interconnection system together with pillars for mounting integrated circuit components is progressively formed layer by layer by successive sequences for each layer, involving using a photo resist to produce a pattern of apertures defining circuit tracks and the pillar positions, depositing metal to form the tracks and the pillars and replacing the remainder of the resist with insulation material. Openings co-operating with the pillars, for the circuit elements are produced during formation of the outermost insulation layer of the circuit system.The circuit elements are mounted on the pillars and the connections between the elements and the printed circuit system are formed by using a further one of said sequences.

Abstract: A Colour Display Apparatus comprises a three-gun cathode ray tube modulated by an input video signal from a digital computer. The video signal contains digital colour codes in the portions of the signal which correspond to blank spaces in the display (e.g. spaces between rows of characters). These codes are stored in a circulating shift and are used to gate the video input to the appropriate combination of guns to produce the required colour for each symbol.