Pub Date : 1973-12-01DOI: 10.1002/J.1538-7305.1973.TB02705.X
B. Puerling, J. T. Roberto
The natural dialogue system (NDS) is a software system designed to permit the easy implementation of time-shared computer programs which employ sophisticated forms of man-machine dialogue to converse with members of a nonprogrammer user audience. The heart of the system is a syntax-directed translator which recognizes user input messages and translates them into an internal text of integers for use by the program. NDS allows the language designer to specify the syntax of the statements in his language, the form of their translations, methods for diagnosing errors in user's input, diagnostic messages to be generated, and the style of dialogue which will exist between the programs and their users. This is accomplished through a dialogue description and a language description consisting of syntactic specification elements with semantic procedures embedded within them. Use of NDS allows the language designer to produce an interactive language which is tailor-made for both his users and his programs. NDS relieves the language designer of the necessity of writing a complex message analyzer, thereby substantially reducing the effort required to produce systems that offer these forms of man-machine dialogue. Furthermore, use of NDS allows such systems to be implemented by less sophisticated programming talent than would otherwise be necessary.
{"title":"Information Management System: The natural dialogue system","authors":"B. Puerling, J. T. Roberto","doi":"10.1002/J.1538-7305.1973.TB02705.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02705.X","url":null,"abstract":"The natural dialogue system (NDS) is a software system designed to permit the easy implementation of time-shared computer programs which employ sophisticated forms of man-machine dialogue to converse with members of a nonprogrammer user audience. The heart of the system is a syntax-directed translator which recognizes user input messages and translates them into an internal text of integers for use by the program. NDS allows the language designer to specify the syntax of the statements in his language, the form of their translations, methods for diagnosing errors in user's input, diagnostic messages to be generated, and the style of dialogue which will exist between the programs and their users. This is accomplished through a dialogue description and a language description consisting of syntactic specification elements with semantic procedures embedded within them. Use of NDS allows the language designer to produce an interactive language which is tailor-made for both his users and his programs. NDS relieves the language designer of the necessity of writing a complex message analyzer, thereby substantially reducing the effort required to produce systems that offer these forms of man-machine dialogue. Furthermore, use of NDS allows such systems to be implemented by less sophisticated programming talent than would otherwise be necessary.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"10 1","pages":"1725-1741"},"PeriodicalIF":0.0,"publicationDate":"1973-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78600068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-12-01DOI: 10.1002/J.1538-7305.1973.TB02711.X
D. Leeper
Analyses in the literature of digital communications often presuppose that the digital source is “white,” that is, that it produces stochastically independent equiprobable symbols. In this paper we show that it is possible to “whiten” to any degree all the first- and second-order statistics of any binary source at the cost of an arbitrarily small controllable error rate. Specifically, we prove that the self-synchronizing digital data scrambler, already shown effective at scrambling strictly periodic data sources, will scramble any binary source to an arbitrarily small first- and second-order probability density imbalance δ if (i) the source is first passed through the equivalent of a symmetric memoryless channel with an arbitrarily small but nonzero error probability ∊, and (ii) the scrambler contains M stages where Some interpretations and applications of this result are included.
{"title":"A universal digital data scrambler","authors":"D. Leeper","doi":"10.1002/J.1538-7305.1973.TB02711.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02711.X","url":null,"abstract":"Analyses in the literature of digital communications often presuppose that the digital source is “white,” that is, that it produces stochastically independent equiprobable symbols. In this paper we show that it is possible to “whiten” to any degree all the first- and second-order statistics of any binary source at the cost of an arbitrarily small controllable error rate. Specifically, we prove that the self-synchronizing digital data scrambler, already shown effective at scrambling strictly periodic data sources, will scramble any binary source to an arbitrarily small first- and second-order probability density imbalance δ if (i) the source is first passed through the equivalent of a symmetric memoryless channel with an arbitrarily small but nonzero error probability ∊, and (ii) the scrambler contains M stages where Some interpretations and applications of this result are included.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"27 1","pages":"1851-1865"},"PeriodicalIF":0.0,"publicationDate":"1973-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84359003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02036.X
H. Heffes, J. M. Holtzman
In trunking theory, peakedness is defined conventionally as the variance-to-mean ratio of a traffic load when carried on an infinite trunk group. For analysis of switching machine delays, it has proven useful to define a peakedness measure associated with the Carried Arrival Process (CAP), the stream of call arrivals carried on an incoming trunk group. The peakedness of the CAP is defined to be the conventional peakedness of a fictitious traffic-load process generated by associating with each carried arrival an independent exponentially distributed holding time with mean equal to the mean of calls actually carried on the trunk group. The problem considered is the effect of trunk group congestion on the peakedness of the CAP for traffic consisting of renewal inputs offered on a blocked-calls-cleared basis to a finite trunk group with exponential holding times. The CAP is characterized as a semi-Markov process. This model leads to the determination of the peakedness of the CAP. Numerical results illustrate the reduction of peakedness, or smoothing, introduced by the congestion.
{"title":"Peakedness of traffic carried by a finite trunk group with renewal input","authors":"H. Heffes, J. M. Holtzman","doi":"10.1002/J.1538-7305.1973.TB02036.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02036.X","url":null,"abstract":"In trunking theory, peakedness is defined conventionally as the variance-to-mean ratio of a traffic load when carried on an infinite trunk group. For analysis of switching machine delays, it has proven useful to define a peakedness measure associated with the Carried Arrival Process (CAP), the stream of call arrivals carried on an incoming trunk group. The peakedness of the CAP is defined to be the conventional peakedness of a fictitious traffic-load process generated by associating with each carried arrival an independent exponentially distributed holding time with mean equal to the mean of calls actually carried on the trunk group. The problem considered is the effect of trunk group congestion on the peakedness of the CAP for traffic consisting of renewal inputs offered on a blocked-calls-cleared basis to a finite trunk group with exponential holding times. The CAP is characterized as a semi-Markov process. This model leads to the determination of the peakedness of the CAP. Numerical results illustrate the reduction of peakedness, or smoothing, introduced by the congestion.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"165 1","pages":"1617-1642"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76000670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02034.X
D. Gloge, Peter W. E. Smith, D. L. Bisbee, E. Chinnock
Cables made from brittle materials like glass require new techniques of end preparation for the purpose of splicing, especially if such splices are to be made in the field. We report here on a method of breaking fibers in a way which invariably produces flat and perpendicular end faces. We explain the underlying theory and derive optimal parameters that permit the design of a simple breaking tool. Experiments with a tool of this kind show that the tolerances for successful fracture are not critical. Laboratory splices of multimode fibers prepared by this method exhibited losses of less than 1 percent (0.04 dB) when joined in index-matching fluid.
{"title":"Optical fiber end preparation for low-loss splices","authors":"D. Gloge, Peter W. E. Smith, D. L. Bisbee, E. Chinnock","doi":"10.1002/J.1538-7305.1973.TB02034.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02034.X","url":null,"abstract":"Cables made from brittle materials like glass require new techniques of end preparation for the purpose of splicing, especially if such splices are to be made in the field. We report here on a method of breaking fibers in a way which invariably produces flat and perpendicular end faces. We explain the underlying theory and derive optimal parameters that permit the design of a simple breaking tool. Experiments with a tool of this kind show that the tolerances for successful fracture are not critical. Laboratory splices of multimode fibers prepared by this method exhibited losses of less than 1 percent (0.04 dB) when joined in index-matching fluid.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"153 1","pages":"1579-1588"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73991317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02029.X
K. Thornber
The incomplete transfer of charge and the existence of random noise lead to the primary operational limitations of charge transfer devices. Owing to the signal dependence of the residual charge, which accumulates as a result of the incomplete transfer, signal detection with static detection levels becomes seriously impaired before the onset of significant signal attenuation or noise degradation. A scheme using dynamic detection levels is found to greatly extend the operational range of CTD's and achieves the minimum possible error rate for detecting uncorrelated charge packet sizes. By contrast, simple coding procedures are found to be ineffective in overcoming signal degradation due to incomplete transfer. Shannon's expression for maximum information transmission capacity is transformed into an expression for maximum information storage capacity. It is found that significantly larger storage capacities are possible with CTD's than have been achieved.
{"title":"Operational limitations of charge transfer devices","authors":"K. Thornber","doi":"10.1002/J.1538-7305.1973.TB02029.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02029.X","url":null,"abstract":"The incomplete transfer of charge and the existence of random noise lead to the primary operational limitations of charge transfer devices. Owing to the signal dependence of the residual charge, which accumulates as a result of the incomplete transfer, signal detection with static detection levels becomes seriously impaired before the onset of significant signal attenuation or noise degradation. A scheme using dynamic detection levels is found to greatly extend the operational range of CTD's and achieves the minimum possible error rate for detecting uncorrelated charge packet sizes. By contrast, simple coding procedures are found to be ineffective in overcoming signal degradation due to incomplete transfer. Shannon's expression for maximum information transmission capacity is transformed into an expression for maximum information storage capacity. It is found that significantly larger storage capacities are possible with CTD's than have been achieved.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"63 3 1","pages":"1453-1482"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82459409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02033.X
D. Gloge, E. Marcatili
New technologies of fiber manufacture and a demand for unusual fiber qualities in communication systems have intensified the interest in a comprehensive theory of multimode fibers with nonuniform index distributions. This paper deals with a general class of circular symmetric profiles which comprise the parabolic distribution and the abrupt core-cladding index step as special cases. We obtain general results of useful simplicity for the impulse response, the mode volume, and the near- and far-field power distributions. We suggest a modified parabolic distribution for best equalization of mode delay differences. The effective width of the resulting impulse is more than four times smaller than that produced by the parabolic profile. Of course, practical manufacturing tolerances are likely to influence this distribution. A relation is derived between the maximum index error and the impulse response.
{"title":"Multimode theory of graded-core fibers","authors":"D. Gloge, E. Marcatili","doi":"10.1002/J.1538-7305.1973.TB02033.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02033.X","url":null,"abstract":"New technologies of fiber manufacture and a demand for unusual fiber qualities in communication systems have intensified the interest in a comprehensive theory of multimode fibers with nonuniform index distributions. This paper deals with a general class of circular symmetric profiles which comprise the parabolic distribution and the abrupt core-cladding index step as special cases. We obtain general results of useful simplicity for the impulse response, the mode volume, and the near- and far-field power distributions. We suggest a modified parabolic distribution for best equalization of mode delay differences. The effective width of the resulting impulse is more than four times smaller than that produced by the parabolic profile. Of course, practical manufacturing tolerances are likely to influence this distribution. A relation is derived between the maximum index error and the impulse response.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"1 1","pages":"1563-1578"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72861879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02032.X
D. Falconer, F. R. Magee
Maximum likelihood data sequence estimation, implemented by a dynamic programming algorithm known as the Viterbi algorithm (VA), is of considerable interest for data transmission in the presence of severe intersymbol interference and additive Gaussian noise. Unfortunately, the required number of receiver operations per data symbol is an exponential function of the duration of the channel impulse response, resulting in unacceptably large receiver complexity for high-speed PAM data transmission on many channels. We propose a linear prefilter to force the overall impulse response of the channel/prefilter combination to approximate a desired truncated impulse response (DIR) of acceptably short duration. Given the duration of the DIR, the prefilter parameters and the DIR itself can be optimized adaptively to minimize the mean-square error between the output of the prefilter and the desired prefilter output, while constraining the energy in the DIR to be fixed. In this work we show that the minimum mean-square error can be expressed as the minimum eigenvalue of a certain channel-dependent matrix, and that the corresponding eigenvector represents the optimum DIR. An adaptive algorithm is developed and successfully tested. The simulations also show that the prefiltering scheme, used together with the VA for two different channel models, compares favorably in performance with another recently proposed prefiltering scheme. Limiting results for the case where the prefilter is considered to be of infinite length are obtained; it is shown that the optimum DIR of length two must be one of two possible impulse responses related to the duobinary impulse response. Finally we obtain limiting results for the case where the transmitting filter is optimized.
{"title":"Adaptive channel memory truncation for maximum likelihood sequence estimation","authors":"D. Falconer, F. R. Magee","doi":"10.1002/J.1538-7305.1973.TB02032.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02032.X","url":null,"abstract":"Maximum likelihood data sequence estimation, implemented by a dynamic programming algorithm known as the Viterbi algorithm (VA), is of considerable interest for data transmission in the presence of severe intersymbol interference and additive Gaussian noise. Unfortunately, the required number of receiver operations per data symbol is an exponential function of the duration of the channel impulse response, resulting in unacceptably large receiver complexity for high-speed PAM data transmission on many channels. We propose a linear prefilter to force the overall impulse response of the channel/prefilter combination to approximate a desired truncated impulse response (DIR) of acceptably short duration. Given the duration of the DIR, the prefilter parameters and the DIR itself can be optimized adaptively to minimize the mean-square error between the output of the prefilter and the desired prefilter output, while constraining the energy in the DIR to be fixed. In this work we show that the minimum mean-square error can be expressed as the minimum eigenvalue of a certain channel-dependent matrix, and that the corresponding eigenvector represents the optimum DIR. An adaptive algorithm is developed and successfully tested. The simulations also show that the prefiltering scheme, used together with the VA for two different channel models, compares favorably in performance with another recently proposed prefiltering scheme. Limiting results for the case where the prefilter is considered to be of infinite length are obtained; it is shown that the optimum DIR of length two must be one of two possible impulse responses related to the duobinary impulse response. Finally we obtain limiting results for the case where the transmitting filter is optimized.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"27 1","pages":"1541-1562"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81169853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02031.X
D. Messerschmitt
{"title":"A Geometric Theory of Intersymbol Interference: Part II: Performance of the Maximum Likelihood Detector","authors":"D. Messerschmitt","doi":"10.1002/J.1538-7305.1973.TB02031.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02031.X","url":null,"abstract":"","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"85 1","pages":"1521-1539"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89692596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02035.X
R. Franks, R. Rishel
An analytic model for the steady-state behavior of an overloaded telephone network is given. The model includes trunk and machine congestion, retrials, “don't answer and busy,” and some network management controls. It is significantly cheaper to use than Monte Carlo simulations for moderate size networks. It compares well with Monte Carlo simulation calculations of point-to-point completion probabilities and the expected number of messages in progress. It compares less well for sender attachment delay and probability of time-out calculations in switching machines.
{"title":"Overload model of telephone network operation","authors":"R. Franks, R. Rishel","doi":"10.1002/J.1538-7305.1973.TB02035.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02035.X","url":null,"abstract":"An analytic model for the steady-state behavior of an overloaded telephone network is given. The model includes trunk and machine congestion, retrials, “don't answer and busy,” and some network management controls. It is significantly cheaper to use than Monte Carlo simulations for moderate size networks. It compares well with Monte Carlo simulation calculations of point-to-point completion probabilities and the expected number of messages in progress. It compares less well for sender attachment delay and probability of time-out calculations in switching machines.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"17 1","pages":"1589-1615"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72835830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1973-11-01DOI: 10.1002/J.1538-7305.1973.TB02030.X
D. Messerschmitt
In a companion paper,1 a geometric approach to the study of intersymbol interference was introduced. In the present paper this approach is applied to the performance analysis of the Viterbi algorithm maximum likelihood detector (MLD) of Forney.2–4 It is shown that a canonical relationship exists between the minimum distance, which Forney has shown determines the performance of the MLD, and the performance and tap-gains of the decision-feedback equalizer (DFE). Upper and lower bounds on the minimum distance are derived, as is an iterative technique for computing it exactly. The performances of the MLD, DFE, and zero-forcing equalizer (ZFE) are compared on the √f channel representative of coaxial cables and some wire pairs. One important conclusion is that, previous statements notwithstanding,2.4 even the MLD experiences a substantial penalty in S/N ratio relative to the isolated pulse bound on this channel of practical interest.
{"title":"A Geometric Theory of Intersymbol Interference","authors":"D. Messerschmitt","doi":"10.1002/J.1538-7305.1973.TB02030.X","DOIUrl":"https://doi.org/10.1002/J.1538-7305.1973.TB02030.X","url":null,"abstract":"In a companion paper,1 a geometric approach to the study of intersymbol interference was introduced. In the present paper this approach is applied to the performance analysis of the Viterbi algorithm maximum likelihood detector (MLD) of Forney.2–4 It is shown that a canonical relationship exists between the minimum distance, which Forney has shown determines the performance of the MLD, and the performance and tap-gains of the decision-feedback equalizer (DFE). Upper and lower bounds on the minimum distance are derived, as is an iterative technique for computing it exactly. The performances of the MLD, DFE, and zero-forcing equalizer (ZFE) are compared on the √f channel representative of coaxial cables and some wire pairs. One important conclusion is that, previous statements notwithstanding,2.4 even the MLD experiences a substantial penalty in S/N ratio relative to the isolated pulse bound on this channel of practical interest.","PeriodicalId":55391,"journal":{"name":"Bell System Technical Journal","volume":"42 1","pages":"1483-1519"},"PeriodicalIF":0.0,"publicationDate":"1973-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87002557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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