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	Pulse-code modulation
		PCM is used in digital telephone systems and for digital audio recording on compact discs.
		Ones-density is often controlled using precoding techniques where the PCM code is expanded into a slightly longer code with a guaranteed bound on ones-density before modulation into the channel.
		In other cases, the long term DC value of the modulated signal is important, as building up a DC offset will tend to bias detector circuits out of their operating range.
	www.ebroadcast.com.au /lookup/encyclopedia/ad/ADPCM.html (462 words)

	Pulse-Code Modulation
		Pulse coding can be performed in a number of ways using conventional circuitry or by means of special cathode ray coding tubes.
		The pdm pulses are then used to gate the output of a precision pulse generator that controls the number of pulses applied to a binary counter.
		Therefore, the clock pulses gated into the binary counter by the pdm pulse may be a number of pulses plus the leading edge of an additional pulse.
	www.tpub.com /neets/book12/49l.htm (1358 words)

	M2M \| GCSE and A-level Physics \| Pulse Code Modulation (Site not responding. Last check: 2007-10-21)
		In Pulse Code Modulation a continuously varying voltage signal is represented by a series of numbers.
		Pulse code modulated signals do not suffer from being degraded because the receiver only has to decide whether the signal was on or off, not how big it was (as it would for an analogue signal).
		PCM is the way that your voice is made into a digital signal when you use your mobile phone.
	www.m2m.ecs.soton.ac.uk /?id=57 (91 words)

	What is Pulse Code Modulation?
		In short, PCM refers to the technique of digitalizing an analog signal by sampling the magnitude of the signal at uniform intervals and converting it into a series of digital or binary code.
		At the receiving end, a pulse code demodulator converts these binary numbers into pulses with the same quantum levels as in the modulator, which are then further processed to obtain the original analog waveform.
		Differential pulse code modulation or Delta pulse code modulation (DPCM) is a technique in which PCM values are encoded as the difference between the current and previous values.
	www.tech-faq.com /pulse-code-modulation.shtml (519 words)

	Compression Algorithms (Site not responding. Last check: 2007-10-21)
		PCM is a term which was formed during the development of digital audio transmission standards.
		PCM doesn`t mean any specific kind of compression, it only implies PAM (pulse amplitude modulation) - quantization by amplitude and quantization by time which means digitalization of the analog signal.
		That means that those coding techniques are lossy, but an important characteristic of this technique is in that it identifies and separate visually relevant and irrelevant parts of an image and then uses appropriate coding techniques for these parts.
	oldwww.rasip.fer.hr /research/compress/algorithms/fund/pcm (2082 words)

	James Mack-Pulse Code Modulation
		PCM and PPM are both encoding methods used for FM signals, and PCM is not a totally different transmission method like AM.
		Therefore, the PCM signal is affected by the same interference as a PPM signal.
		Firstly, PCM radios send what is known as a "checksum", which adds redundancy to the system by allowing the receiver to check that the data it is receiving is not corrupt.
	www.jmack.net /html/rcmodels/pulsecode (2101 words)

	Pulse Code Modulation
		Pulse code modulation (to be discussed in depth later) is the heart of technology in communications in today’s digital world.
		The stream of pulses and non-pulse streams of 1’s and 0’s are not easily affected by interference and noise.
		One disadvantage of PCM is that the signal accuracy is reduced because of the quantizing of the samples.
	cbdd.wsu.edu /kewlcontent/cdoutput/TR502/page13.htm (494 words)

	PCM Details (Site not responding. Last check: 2007-10-21)
		PCM is a Time-Domain Waveform coding method and is defined within CCITT G.711, and AT&T 43801.
		In both A-Law and Mu-Law PCM, the values used to represent the amplitude is a number between 0 and +/- 127; therefore, 8 bits are required to represent each sample (2 to the eigth power = 256).
		Note that the bit pattern for Mu-Law PCM is such that bit two is a zero for all eight bytes.
	telecom.tbi.net /pcm1.html (602 words)

	Heritage (Site not responding. Last check: 2007-10-21)
		However, PCM could not be made practical at that time for 2 main reasons: 1) It needs much more frequency space than analog transmission, and 2) It requires a precision and speed of operation that could not be achieved at reasonable cost with the devices then available.
		Advantages: PCM repeaters simple regenerate enfeebled pulses and there are no accumulating increments of distortion as this process is repeated on a long line.
		Using PCM or similar codes to convert analog/ continuous signals to digital form, systems of this type now carry as many as 96 phone calls over a single pair of wires.
	www.bell-labs.com /org/1133/Heritage/Pcm (369 words)

	Pulse-code modulation - Wikipedia, the free encyclopedia
		Pulse-code modulation (PCM) is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals, then quantized to a series of symbols in a digital (usually binary) code.
		PCM has been used in digital telephone systems and is also the standard form for digital audio in computers and the compact disc red book format.
		This perhaps is a natural consequence of this technique having evolved alongside two others, Pulse width modulation and Pulse position modulation, in which the information to be encoded is in fact represented by binary signal pulses of varying width or position, respectively.
	en.wikipedia.org /wiki/Pulse-code_modulation (1787 words)

	Pulse-code modulation
		Several PCM streams may be multiplexed into a larger aggregate data stream, this technique is called Time-Division Multiplexing or TDM.
		Ones-density is often controlled using precoding techniques such as Run Length Limited, where the PCM code is expanded into a slightly longer code with a guaranteed bound on ones-density before modulation into the channel.
		The first transmission of speech by pulse code modulation was the SIGSALY voice encryption equipment used for high-level Allied communications during World War II.
	www.camcity.co.uk /directory-articles/PCM (863 words)

	Define DPCM - Differential Pulse Code Modulation
		“Differential pulse-code modulation (DPCM): Pulse-code modulation in which an analog signal is sampled and the difference between the actual value of each sample and its predicted value, derived from the previous sample or samples, is quantized and converted, by encoding, to a digital signal.
		Differential PCM (DPCM) is designed to calculate this difference and then transmit this small difference signal instead of the entire input sample signal.
		Differential pulse code modulation of broadcast-rate television signals by Theodore Michael Lyszczarz
	www.birds-eye.net /definition/d/dpcm-differential_pulse_code_modulation.shtml (743 words)

	pulse-code modulation
		In physics, a form of digital modulation in which microwaves or light waves (the carrier waves) are switched on and off in pulses of varying length according to a binary code.
		It is a relatively simple matter to transmit data that are already in binary code, such as those used by computer, by these means.
		The value of the amplitude is then converted into a binary code for transmission on the carrier wave.
	www.tiscali.co.uk /reference/encyclopaedia/hutchinson/m0031099.html (254 words)

	Pulse Code Modulation - Why? (Site not responding. Last check: 2007-10-21)
		This type of modulation is used as the first step in converting an analog signal to a discrete signal or in cases where it may be difficult to change the frequency or phase of the carrier.
		In this case the carrier is a pulse train rather than a sine wave and the spectrum of the carrier consists of several components at nwc = 2np/T where T is the time between pulses.
		This form of modulation is often used in control applications as the average value is proportional to the pulse width.
	www.co.umist.ac.uk /misc/ct211/coursework/NewFolder/PCM_Site/why.htm (536 words)

	PCM (Pulse Code Modulation) - DVD Audio Sampling Techniques (Site not responding. Last check: 2007-10-21)
		PCM or Pulse Code Modulation has become the de facto standard for digitally encoding analogue signals in both computer software and home theater audio applications.
		PCM's method divides an analogue voltage into regular increments and assigns a binary number (a "pulse code") to each cycle.
		PCM rose to the prominence it enjoys today when it was chosen as the audio digitization method for the Compact Disc.
	www.hometheaterfocus.com /dvd/pcm.aspx (369 words)

	What is pulse code modulation? - a definition from Whatis.com - see also: PCM (Site not responding. Last check: 2007-10-21)
		To obtain PCM from an analog waveform at the source (transmitter end) of a communications circuit, the analog signal amplitude is sampled (measured) at regular time intervals.
		The output of a pulse code modulator is thus a series of binary numbers, each represented by some power of 2 bits.
		At the destination (receiver end) of the communications circuit, a pulse code demodulator converts the binary numbers back into pulses having the same quantum levels as those in the modulator.
	searchnetworking.techtarget.com /sDefinition/0,,sid7_gci214284,00.html (331 words)

	ALSA project - the C library reference: PCM (digital audio) interface
		Although abbreviation PCM stands for Pulse Code Modulation, we are understanding it as general digital audio processing with volume samples generated in continuous time periods.
		The ALSA PCM API uses a different behaviour when the device is opened with blocked or non-blocked mode.
		The PCM device has accepted communication parameters and it is waiting for snd_pcm_prepare() call to prepare the hardware for selected operation (playback or capture).
	www.alsa-project.org /alsa-doc/alsa-lib/pcm.html (2875 words)

	Optimal Pulse Code Modulation (oPCM) and its application as an audio quality parameter
		Standard digital sound is stored as PCM data (pulse code modulation): The audio signal is measured at a fixed rate ("sampling rate") with a given precision ("resolution").
		Since there are two parameters that define a PCM file (sampling rate and resolution) the best combination of these two values has to be worked out.
		This is how optimal PCM (oPCM) streams are defined: They are the best compromise between sampling rate and resolution at a fixed bitrate.
	cips02.physik.uni-bonn.de /~scheller/audio/main.html (1423 words)

	ADPCM - Adaptive Differential Pulse Code Modulation
		A coding method in which the difference between consecutive LPCM samples is coded--it is more bit-efficient than LPCM coding.
		Full Name: Adaptive Differential Pulse Code Modulation Description:It is a PCM encoding technique by which analog voice samples are encoded into high-quality digital signals.
		Adaptive Differential Pulse Code Modulation process by which analog voice samples are encoded into high-quality digital signals.
	www.auditmypc.com /acronym/ADPCM.asp (474 words)

	ADPCM Codecs (Site not responding. Last check: 2007-10-21)
		Adaptive Differential Pulse Code Modulation (ADPCM) codecs are waveform codecs which instead of quantizing the speech signal directly, like PCM codecs, quantize the difference between the speech signal and a prediction that has been made of the speech signal.
		Code for various ADPCM codecs, as well as the G711 A-law and u-law PCM, was released into the public domain by Sun Microsystems, Inc. Its available for FTP here.
		Also various patches for this code, including an extension to allow it to operate at 16 kbits/s, are available from the same FTP site.
	www-mobile.ecs.soton.ac.uk /speech_codecs/standards/adpcm.html (247 words)

	DPCM - Differential Pulse Code Modulation (Site not responding. Last check: 2007-10-21)
		PCM (Pulse Code Modulation) permits adjacent samples to be described from extreme opposite ends of the sample range.
		As this situation rarely occurs it should be able to convey the baseband data using fewer bits.
		DPCM allows this to be achieved by describing only the changes between the samples.
	www.mpirical.com /companion/Transmission/DPCMModulation.htm (49 words)

	Definition: pulse-code modulation (Site not responding. Last check: 2007-10-21)
		pulse-code modulation (PCM): Modulation in which a signal is sampled, and the magnitude (with respect to a fixed reference) of each sample is quantized and digitized for transmission over a common transmission medium.
		Note 1: In conventional PCM, before being digitized, the analog data may be processed (e.g., compressed), but once digitized, the PCM signal is not subjected to further processing (e.g., digital compaction) before being multiplexed into the aggregate data stream.
		Note 2: PCM pulse trains may be interleaved with pulse trains from other channels.
	www.atis.org /tg2k/_pulse-code_modulation.html (123 words)

	Differential pulse code modulation transmission system - Patent 4477915
		Differential pulse code modulation transmission system comprising a transmitter and a receiver.
		In the transmitter there is subtracted from an information signal x(n) to be transmitted, a prediction signal y(n) for the purpose of generating a difference signal e(n), which is quantized and converted into a quantized difference signal in a quantizing arrangement 6.
		This analog-to-digital converter 3 is controlled by sampling pulses which occur at a period T. This digital video signal x(n) now represents the information signal to be transmitted to an associated receiver.
	www.freepatentsonline.com /4477915.html (4918 words)

	Pulse-Code Modulation
		A current source is used to apply the pcm pulses to an RC circuit, such as that
		At T1 the pulse corresponding to the least significant digit is applied and C1 charges to 16 volts.
		The pulse at T3 increases the charge on C1 by 16 volts to a total charge of 28 volts.
	www.tpub.com /content/neets/14184/css/14184_178.htm (362 words)

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