pulse-codemodulation has been used on an increasingly broad scale in telecommunications over the past few years. This article describes integrated codec devices that considerably simplify the design of PCM systems. S...
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pulse-codemodulation has been used on an increasingly broad scale in telecommunications over the past few years. This article describes integrated codec devices that considerably simplify the design of PCM systems. Some examples of applications are also given.
Maintaining a specific error rate as a quality criterion in digital communications results in the case of fixed pulse shape, in the requirement for optimum reception filters in recepters. Various optimization techniqu...
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Maintaining a specific error rate as a quality criterion in digital communications results in the case of fixed pulse shape, in the requirement for optimum reception filters in recepters. Various optimization techniques are reviewed;a modified signal/noise ratio is used as a quality criterion.
The practice of using the signal-to-noise ratio improvement (SNRI) or the signal-to-prediction error ratio (SPER) as performance indicators for optimizing the predictor in differential pulse code modulation (DPCM) sys...
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The practice of using the signal-to-noise ratio improvement (SNRI) or the signal-to-prediction error ratio (SPER) as performance indicators for optimizing the predictor in differential pulse code modulation (DPCM) systems is examined. By reconsidering the relationship between signal-to-quantization noise ratio (SNR) and SNRI, it is shown that optimizing the predictor by maximizing the SNRI can produce a change in output SNR that is much greater than or much less than the increase in SNRI. The cause of the discrepancy is that optimizing the predictor may produce a change in the prediction error probability density function (pdf), which is the quantizer input. The change in the quantizer input pdf can yield an increase or decrease in the quantizer output noise power even if the quantizer is reoptimized.
State-of-the-art pulse code modulation (PCM) systems can effectively deal with the problems of rapid communications expansion. As a result of modern digital implementation techniques, PCM systems are inherently reliab...
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State-of-the-art pulse code modulation (PCM) systems can effectively deal with the problems of rapid communications expansion. As a result of modern digital implementation techniques, PCM systems are inherently reliable and stable. One introduced into a telephone network. PCM systems can easily be added to meet present of future requirements.
A DPCM system for storage or transmission (via noiseless channel) of moving (3-D) TV images is presented. The fully nonlinear (adaptive) DPCM system based on a composite model of the image fragment is described. The d...
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A DPCM system for storage or transmission (via noiseless channel) of moving (3-D) TV images is presented. The fully nonlinear (adaptive) DPCM system based on a composite model of the image fragment is described. The description takes into consideration mutual influence of the prediction and quantization parts of the system. The paper also establishes two types of system optimization: a) minimization of the mean square quantization error (MSQE);b) minimization of the MSQE when the entropy of the quantizer output is below a specified level. The results of the optimization provide the parameters of the system.
This discussion of the practical design of digital tone sources presents examples of both one and two-frequency tones, reduction of samples by frequency adjustment and symmetry, offset samples, and a program for tone ...
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This discussion of the practical design of digital tone sources presents examples of both one and two-frequency tones, reduction of samples by frequency adjustment and symmetry, offset samples, and a program for tone sample calculations.
In a data-acquisition system, analog signals with bandwidths below 5 kHz are often best handled with pulse-codemodulation (PCM) techniques. PCM offers many advantages: data are stored in digital form, thus guaranteei...
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In a data-acquisition system, analog signals with bandwidths below 5 kHz are often best handled with pulse-codemodulation (PCM) techniques. PCM offers many advantages: data are stored in digital form, thus guaranteeing accurate reproduction of recorded signals;the signal-to-noise ratio is better than 70 db (about double that of many fm or direct recording methods);and the accuracy of recorded information is within 0. 1% (about and order of magnitude better than most other methods). PCM requires that analog signals be sampled at regular, discrete intervals and that the signal amplitudes be coded into a digital format. Even though most data-acquisition applications are analog, to maintain accuracy and ease data manipulation it is better to encode the data digitally before recording. This ensures that the desired signals are truly recorded and regenerated. PCM systems are typically 0. 1 to 0. 025% accurate - or even better, depending on the converter used.
Part 1 of this article explained why the British Post Office has adopted a 30-channel pulse-codemodulation standard, and included a technical description of the multiplex equipment. This part describes the operating ...
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Part 1 of this article explained why the British Post Office has adopted a 30-channel pulse-codemodulation standard, and included a technical description of the multiplex equipment. This part describes the operating principles, equipment, and installation of the associated 2. 048 Mbit/s digital line system.
Accurate qualification of the PCM terminal requires separate measurements between the analog interface audio input-output) and the digital interface (2 Mbits/sec emission and reception) in both directions: transmit, f...
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Accurate qualification of the PCM terminal requires separate measurements between the analog interface audio input-output) and the digital interface (2 Mbits/sec emission and reception) in both directions: transmit, from analog input to digital emission; receive, from digital reception to analog output. The TEKELEC TE 80 PCM test set has been designed for that purpose. The instrument is fully automatic; able to handle the intermediate data and to deliver a final result directly usable by the operator; and easy to use.
Accurate qualification of the PCM terminal requires separate measurements between the analog interface audio input-output) and the digital interface (2 Mbits/sec emission and reception) in both directions: transmit, f...
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Accurate qualification of the PCM terminal requires separate measurements between the analog interface audio input-output) and the digital interface (2 Mbits/sec emission and reception) in both directions: transmit, from analog input to digital emission;receive, from digital reception to analog output. The TEKELEC TE 80 PCM test set has been designed for that purpose. The instrument is fully automatic;able to handle the intermediate data and to deliver a final result directly usable by the operator;and easy to use.
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