* Pulse-amplitude modulation ( PAM )

Pulse-amplitude modulation, acronym PAM, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.

Pulse-amplitude modulation is widely used in baseband transmission of digital data, with non-baseband applications having been largely replaced by pulse-code modulation, and, more recently, by pulse-position modulation.

Pulse-amplitude modulation has also been developed for the control of light-emitting diodes ( LEDs ), especially for lighting applications.

it: Pulse-amplitude modulation

* Pulse-amplitude modulation

* Pulse-amplitude modulation, a characteristic of pulsed signals

LED drivers based on the PAM technique offer improved energy efficiency over systems based upon other common driver modulation techniques such as pulse-width modulation ( PWM ) as the forward current passing through an LED is relative to the intensity of the light output and the LED efficiency increases as the forward current is reduced.

LED backlights are often dimmed by applying pulse-width modulation to the supply current, switching the backlight off and on again like a fast strobe light.

Several programs, including MP ( Module Player, 1989 ), ScreamTracker, Fast Tracker, Impulse Tracker, and even device drivers for Linux and Microsoft Windows, could play pulse-code modulation ( PCM ) sound through the PC speaker using special techniques explained later in this article.

Including a copper cap on the pole piece or a copper shorting ring on it, can reduce the increase in impedance seen at higher frequencies in typical drivers, and also reduce the nonlinearity due to inductance modulation.

The company developed the world's first 600dpi that retailed under £ 1000 ( it purchased printer engines from Canon Inc, and using its own drivers and laser modulation techniques ( hardware and software ) was able to increase the resolution to 600dpi.

Examples of hardware noise reduction are the use of shielded cable, analog filtering, and signal modulation.

Additionally, PWM ( pulse-width modulation ) anemometers are also used, wherein the velocity is inferred by the time length of a repeating pulse of current that brings the wire up to a specified resistance and then stops until a threshold " floor " is reached, at which time the pulse is sent again.

Sodium, calcium, and potassium channels are all implicated in contributing to input modulation.

This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, including extraction of modulation from radio signals in radio receivers — these diodes are forms of rectifiers.

The most popular are Gilbert cell mixers, diode mixers, diode ring mixers ( ring modulation ) and switching mixers.

While there is currently no consensus on how to categorize effects, the following are seven common classifications: distortion, dynamics, filter, modulation, pitch / frequency, time-based and feedback / sustain.

Several different telephone line modulation techniques are used by fax machines.

The carrier and sideband amplitudes are illustrated for different modulation indices of FM signals.

Other immunomodulating substances, such as drugs that prevent acetylcholine receptor modulation by the immune system, are currently being researched.

Analog and digital modulation facilitate frequency division multiplexing ( FDM ), where several low pass information signals are transferred simultaneously over the same shared physical medium, using separate passband channels ( several different carrier frequencies ).

Common analog modulation techniques are:

The changes in the carrier signal are chosen from a finite number of M alternative symbols ( the modulation alphabet ).

The most fundamental digital modulation techniques are based on keying:

* In the case of QAM ( quadrature amplitude modulation ), a finite number of at least two phases, and at least two amplitudes are used.

Digital modulation schemes are possible because the transmitter-receiver pair have prior knowledge of how data is encoded and represented in the communications system.

In this case, modulation symbols ( rather than bits, characters, or data packets ) are asynchronously transferred.

The most common digital modulation techniques are:

MSK and GMSK are particular cases of continuous phase modulation.

Nevertheless, even though switching amplifiers are completely unsuitable for normal QAM constellations, often the QAM modulation principle are used to drive switching amplifiers with these FM and other waveforms, and sometimes QAM demodulators are used to receive the signals put out by these switching amplifiers.

These are not modulation schemes in the conventional sense since they are not channel coding schemes, but should be considered as source coding schemes, and in some cases analog-to-digital conversion techniques.

* Space modulation A method whereby signals are modulated within airspace, such as that used in Instrument landing systems.

The modulated waves are summed, and the resulting waveform is a combination of both phase-shift keying ( PSK ) and amplitude-shift keying ( ASK ), or ( in the analog case ) of phase modulation ( PM ) and amplitude modulation.

They can be considered the successors of early telephotography input devices, which were able to send consecutive scan lines as analog amplitude modulation signals through standard telephonic lines to appropriate receivers ; such systems were in use in press since the 1920s to the mid 1990s.

Further, another design goal was to be able to easily incorporate new coding and modulation standards in the future, so that military communications can keep pace with advances in coding and modulation techniques.

The BTSs are equipped with radios that are able to modulate layer 1 of interface Um ; for GSM 2G + the modulation type is Gaussian minimum-shift keying ( GMSK ), while for EDGE-enabled networks it is GMSK and 8-PSK.

The red beam has a tunable filter called CRisp Imaging SpectroPolarimeter ( CRISP ) which operates from 510 to 860 nm and is able to measure polarization by using liquid crystal modulation combined with a polarizing beamsplitter.

Given that each analogue channel occupies 6 MHz of bandwidth, Cogeco utilizes the latest compression, multiplexing and modulation technologies to be able to transmit up to 13 Standard Definition TV signals or else up to 3 High Definition TV signals on each of these channels.

No systematic effect or side reaction able to account for the observed modulation amplitude and to simultaneously

Domo is able to learn about its own sensorimotor abilities and is able to fine-tune the modulation of its actions based on previously accomplished tasks.

Since each pair of devices uses a different modulation scheme for communication, other devices may not be able to demodulate the information sent between them.

This flexibility is also required for being able to dynamically adjust the bandwidth, modulation and coding schemes.

Switching to frequency modulation ( FM ) solved this problem, which is better able to discriminate the distance without being further confused by the image size.

By 1950 the small team at Ferranti Canada had built a working pulse-code modulation ( PCM ) radio system that was able to transmit digitized radar data over long distances.