Showing papers on "Code word published in 1976"

Flexible Coding in Word Recognition.

Abstract: An experiment was designed to examine the contribution of phonetic information in the processing of words in tachistoscopic recognition masking. Following stimulus presentation, subjects were required to indicate which of two alternatives had appeared. On trials containing word stimuli, the alternatives were either phonetically identical (SENT, CENT) or not (SOLD, COLD). Recognition performance was inferior in the former case, provided conditions were not structured to discourage reliance on phonetic information. The findings were interpreted as showing that more than one type of coding process can underly the word superiority effect. Phonetic information is ordinarily used to code words in this type of task, but an alternative processing tactic (e.g., one relying on visual or perhaps semantic codes) can also be effectively used in word recognition when phonetic information does not discriminate well among response alternatives.

Code Generation for a One-Register Machine

Abstract: The majority of computers that have been built have performed all computations in devices called accumulators, or registers. In this paper, it is shown that the problem of generating minimal-length code for such machines is hard in a precise sense; specifically it is shown that the problem is NP-complete. The result is true even when the programs being translated are arithmetic expressions. Admittedly, the expressions in question can become complicated.

Method for digital run-length coding with redundance reduction for transmission of binarily coded picture informations

Abstract: Method for the digital run-length coding with redundance reduction for the transmission of binary-coded picture information, whereby short code words are assigned to run lengths which occur often, and long code words are assigned to rare run lengths and whereby, from a given run length on, a prefix word for the differentiation of code words of the shorter run-lengths is assigned to the run-lengths, as well as a code word following the prefix word and stating the respective run-lengths as a binary number Black and white run-lengths which are transmitted by a code word are associated with different code words, depending on how often they occur The given run-length, from which the coding is to be done with the help of a prefix word, is different for black and white run-lengths An individual code word is transmitted at the beginning of a line, and it differs from the code words for the individual run-lengths, from the word combination resulting from the prefix word and the subsequent code words, and which does not occur as bit combination of several words or partial words, respectively, in the transmitted data flow

Syndrome Decoding of Binary Rate-1/2 Convolutional Codes

Abstract: The classical Viterbi decoder recursively finds the trellis path (code word) closest to the received data. Given the received data, the syndrome decoder first forms a syndrome instead. Having found the syndrome, that only depends on the channel noise, a recursive algorithm like Viterbi's determines the noise sequence of minimum Hamming weight that can he a possible cause of this syndrome. Given the estimate of the noise sequence, one derives an estimate of the original data sequence. The bit error probability of the syndrome decoder is no different from that of the classical Viterbi decoder. However, for short constraint length codes the syndrome decoder can be implemented using a read-only memory (ROM), thus obtaining a considerable saving in hardware. The syndrome decoder has at most \frac{3}{4} as many path registers as does the Viterbi decoder. There exist convolutional codes for which the number of path registers can be even further reduced.

Method and arrangement for reducing the bandwidth and/or time required to transmit a dithered image

Abstract: An image is scanned and dither processed in picture element groups of predetermined size, each corresponding to a group of cells of a remotely located display panel. As each picture element group is scanned, the pattern represented by the corresponding dithered image bits is compared to a dictionary of patterns stored in a first memory. If the pattern is not among those then in the memory, it is assigned an associated code word and is entered into the memory. In addition, both the pattern and its code word are transmitted to the remote location. They are there stored in a second memory, and individual cells of the cell group corresponding to the scanned picture elements are energized in accordance with the pattern. If, on the other hand, a scanned pattern is the same as one already stored in the first memory, only the code word associated with that pattern is transmitted to the remote location. The code word is used at the remote location to retrieve the associated pattern from the second memory when it is displayed at the corresponding cell group of the display panel.

Adaptive digital coder and decoder

Abstract: An adaptive coder and decoder for reducing the bit rate required to trans digitally encoded speech signals. The invention relies on the fact that the speech pattern of the average talker contains significant numbers of inter-syllable and inter-word pauses. The coder includes circuitry that monitors the idle pattern code generated by the coder's analog-to-digital converter and a code word generator that generates one or more special code words that are substituted for idle pattern code sequences of predetermined length. The speech signal and special code words are then fed into an elastic buffer and transmitted to the distant receiver at a lower bit rate than was employed for the encoding process. At the receiving location, the decoder recognizes the special code words, substitutes an idle pattern bit stream of the appropriate length for the code words and then reads-out the contents of an elastic input buffer at a higher bit rate than was used to transmit the incoming signal, that is, at the same bit rate as was initially used at the coder.

Cross-correlation arrangement

Abstract: Cross-correlation arrangement for determining the presence or absence of a signal x 2 (t) of known frequency in an unknown signal x 1 (t) if this signal x 2 (t) is present for at least a period of time τ o with an unknown starting instant. An auxiliary signal a 1 (t) is added to the signal x 2 (t). The sum signal is converted into one-bit code words s(nT) which are multiplied in at least a first correlation channel by one-bit code words y per (kT) which are stored in a storage medium having at least N/2 addressable storage locations. The code words y per (kT) are elements of a series {y per (kT)} which is formed by the code words which occur in a predetermined time interval having a length NT and which are of a non-periodical signal of the form sign [x 2 (t) + a 2 (t)]. The product code words obtained are added together in an integrator. This integrator is read each time after a time interval NT and reset. The absolute value of an output code word of the integrator is optionally added to corresponding code words of other correlation channels. The sum code words obtained in this way are integrated in a second integrator whose contents is continuously compared with a detection level. If N o = τ o /T, N is smaller than N o for example a factor of 3. The value of N determines the width of the detection characteristic.

Best match content addressable memory

Abstract: A method of and an apparatus for determining the best match, i.e., minimum Hamming distance, between a search word and a plurality of file words is disclosed. The method involves simultaneously comparing the search word to a file word and to a match word. If the comparison indicates that the file word is a better match than the match word, the file word becomes the match word and the next file word is compared to the new match word. The operation continues until all the file words have been operated upon such that the last match word becomes the best match word.

Wireless paging receiver

Abstract: A wireless paging receiver to be called up individually or as member of a group of receivers by a binary modulated carrier frequency call telegram. Each call telegram contains an address. Each individual address is composed by code words selected from a certain number of patterns. In a group call address one or more code words are replaced by a group call pattern, so that all receivers are called whose addresses contain the remaining code word patterns. For coding the address in the receiver only one connection must be positioned for each address code word. Messages can be transmitted with the call telegram and different call signals of different lengths generated. A parity check of the received call telegram is performed with little additional material.

Audio-visual programmer

Abstract: A multimedia motion picture and photographic slide projection control apparatus which permits a plurality of projector devices to be controlled from an operator's console. Manually operable switch means, operating through digital control means, develops a Program Command Code Word for each change in switch conditions, the control word being decoded to provide an ON/OFF response by selected projectors, as well as lamp dissolve rate response. Simultaneously, the Program Command Code Words are recorded on a magnetic tape such that when a given presentation has been developed to the satisfaction of the operator, the stored command words can be used to control the projection devices to provide repetitive performances of the same audio-visual presentation.

PCM telecommunication system with merger of two bit streams along a common signal path

Abstract: A transmitting terminal, communicating via a PCM link with a remote receiving terminal, processes two simultaneously arriving bit streams consisting of recurrent frames of 32 time slots, 29 of these time slots containing 8-bit code words which represent voice samples from as many PCM channels. The two arriving bit streams are transcoded by an ADPCM (adaptive differential pulse-code modulation) technique to convert the 8-bit words into substantially equivalent 4-bit words which are then combined, in interleaved relationship, into a single bit stream sent to the receiving terminal, each frame of this composite bit stream having 29 of its 32 time slots occupied by two four-bit words respectively taken from the original bit streams. At the receiving terminal a complementary procedure is followed to separate the two groups of 4-bit code words from each other and to reconvert each of them into an 8-bit word, with substantial reconstitution of the original bit streams.

Selective calling circuit

Abstract: A selective calling circuit includes a central control code generator for generating a digital stream having repetitions of selected code words of digital information for selectively calling a plurality of remote receiving stations in this circuit. Each remote station includes a decoder for recognizing a predetermined sequence of digital information and reconstructing selected digital code words included therein. A variable modulus counter, responsive to clock pulses and means for selectively varying the modulus of the counter, is included in the code generator at the central control station. A resettable counter that counts in response to clock pulses and is reset in response to received code signals is included in the decoder at the remote station.

Reverberation compensating communication system

Abstract: A system for transmitting a signal through a reverberant environment characterized by multipath communication which causes dispersion and fading of the signal. The signal is phase modulated onto a carrier which is also modulated by a repeating series of digital pseudo noise code words. The length of each word is equal to the length of a symbol of the signal and synchronized thereto, individual symbols being of shorter duration than the signal fading time. A receiver views symbols via a selector switch which serves as a window for successively viewing portions of substantially identical reverberation patterns of each symbol. A set of matched filters coupled to the selector switch sequentially demodulates the code words to provide a repeating sequence of pulses of amplitude modulated carrier these amplitude modulated pulses having symbol data thereon and being applied to a delay locked loop for the generation of a reference signal for recovering the symbols.

Detecting the Presence of Speech Using ADPCM Coding

Abstract: When speech is coded using a differential pulse-code modulation system with an adaptive quantizer, the digital code words exhibit considerable variation among all quantization levels during both voiced and unvoiced speech intervals. However, because of limits on the range of step sizes, during silent intervals the code words vary only slightly among the smallest quantization steps. Based on this principle, a simple algorithm for locating the beginning and end of a speech utterance has been developed. This algorithm has been tested in computer simulations and has been constructed with standard integrated circuit technology.

Code word determination

Abstract: A method and circuit for determining a unique word contained in received signals in a transmission system which operates with a multiple phase type of modulation at the transmitter and coherent demodulation at the receiver, the unique word being transmitted only as signals in two phases which are 180° apart and the received signals being divided into orthogonal voltage components during demodulation, a single value whose algebraic sign is indicative of the unique word being derived by dividing the orthogonal components to form a quotient signal representative of the ratio therebetween, integrating the quotient signal over a plurality of clock pulse periods, multiplying the integrated quotient signal with one of the orthogonal components, and adding the resultant product signal to the other orthogonal component to form the single value.

Code word detecting method

Abstract: A method for detecting a predetermined code word contained in received signals in a transmission system which operates with a four-phase type of modulation at the transmitter and coherent demodulation at the receiver, the code word being transmitted only as signals in two phases which are 180° apart and the received signals being divided into orthogonal voltage components during demodulation, which method includes selecting that one of the sum and difference of the voltage components which has the larger absolute magnitude value, and evaluating the received signal in accordance with the algebraic sign of that one of the sum and difference which is thus selected.

Electronic circuits for sewing machines

Abstract: A control unit for a sewing machine includes a mechanism for mechanically positioning the stitch-forming members and a pattern memory unit for controlling this mechanism, from which stitch position detemining code words belonging to a specific pattern can be selected by the operator. The code word for determining a stitch position is read from the pattern memory into a shift register. The shift register is shifted in relation to the movement of the main shaft of the sewing machine so that code words for each successive stitch of a pattern are successively made available to the mechanical positioning mechanism. The succession of code words in a pattern can be recirculated in the shift register at the end of a pattern cycle, for repetition of the pattern.

Circuit for converting a companded digital time-amplitude pulse code into a linear digital amplitude pulse code

Abstract: A shift-companded, or n:m, pulse code, representing on a time-amplitude basis the information of a conventional, amplitude companded, pulse code, is converted to a linear, digital, amplitude, pulse code by first converting the shift-companded amplitude information into 2s-complement form with a number of bits sufficient to yield substantially the same resolution of the encoded information as did the shift-companded code form. Thereafter half of the 2s-complement code words are loaded into an accumulator to be averaged. The resulting digital word representing the average is in 2s-complement, linear PCM format and is thus readily useful for data processing or for further conversion to a commercial, companded, transmission code.

Code generating keyboard apparatus - contains two switching elements controlled by selection signals produced by pressing keys

Abstract: The generator is used to produce a "one from ten" code and when a key in a keyboard is operated, the selection signal generated controls a first and a second switching element the first switching element forms a first part of a codeword with pref five bits, of which one has a logic state which is different from that of the others a coding device forms the second part of the codeword with 5 bits with a specified state distribution the device also combines the first codeword part with its second part, depending on the signal stored in the second element

Comma-free codes and incidence algebras

Abstract: A code which does not require a distinct symbol to separate code words is called comma-free. We study comma-free codes with words of length 2 by considering the binary relation the code defines on its alphabet. If the code is a maximal comma-free code we show that the relation it defines is the support relation of an incidence algebra and its complementary relation will also define an incidence algebra.

Multiple-cyclic codes

Abstract: Most of the important codes fall in the category of cyclic codes. However the study of cyclic codes is confined to considering overall cyclic shifts of code vectors. Also the study of random-error correction is being made in a setting which is in fact unrealistic, because as the length of the code words increases the number of possible random errors also increases; the number of increased random errors is to be naturally found in the increased part of the word length. Thus practical considerations lead us to think that random errors are suitably phased over the word length. In this paper the phasing aspects are considered in terms of cyclic blocks so that a code word is composed of several blocks, each block having a cyclic structure. Polynomial representations are developed under a new algebraic setting. A characterization theorem, matrix description, and representation in terms of roots in some known field arc provided.

Variable Length Encoding of Binary Memoryless Sources with a Fidelity Measure

Abstract: This concise paper deals with variable length source coding for binary memoryless sources with a fidelity criterion. The encoding scheme under consideration is an ( M_{c}, N, K ) code consisting of a distortionless run-length inner code of size M c and an outer code that maps each source vector of length N to a codeword of length less than or equal to K . The encoding of the outer code is accomplished by means of a trellis search, and the distortion measure used is a Hamming distance. For composite binary memoryless sources an adaptive ( M_{c}, N ) code can be constructed by varying the constraint K on codeword length according to the source statistics. The ( M_{c}, N, K ), and ( M_{c}, N ) codes are insensitive to the inaccuracy in estimating the source probabilities. Rate-distortion curves, obtained by computer simulation, are plotted along with the theoretical rate-distortion function R(D) .