A channel actually consists of two signals: the picture information is transmitted using amplitude modulation on one frequency, and the sound is transmitted with frequency modulation at a frequency at a fixed offset ( typically 4. 5 to 6 MHz ) from the picture signal.

In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted.

In telecommunications, modulation is the process of conveying a message signal, for example a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted.

The undesired signals are removed by the IF bandpass filter, leaving only the desired offset IF signal at f < small >< sub > IF </ sub ></ small > which contains the original modulation ( transmitted information ) as the received radio signal had at f < small >< sub > d </ sub ></ small >.

In bit-synchronous operation, clock timing is usually delivered at twice the modulation rate, and one bit is transmitted or received during each clock cycle.

# In facsimile systems using amplitude modulation, that form of transmission in which the maximum transmitted power corresponds to the maximum density of the subject.

# In facsimile systems using frequency modulation, that form of transmission in which the lowest transmitted frequency corresponds to the maximum density of the subject.

In delta modulation, the transmitted data is reduced to a 1-bit data stream.

In the double-sideband suppressed-carrier transmission ( DSB-SC ) modulation, unlike AM, the wave carrier is not transmitted ; thus, a great percentage of power that is dedicated to it is distributed between the sidebands, which implies an increase of the cover in DSB-SC, compared to AM, for the same power used.

The high-frequency signal components are emphasized to produce a more equal modulation index for the transmitted frequency spectrum, and therefore a better signal-to-noise ratio for the entire frequency range.

Frequency-shift keying ( FSK ) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave.

* It eliminates the dependence of a signal's power spectrum upon the actual transmitted data, making it more dispersed to meet maximum power spectral density requirements ( because if the power is concentrated in a narrow frequency band, it can interfere with adjacent channels due to the cross modulation and the intermodulation caused by non-linearities of the receiving tract ).

For example, in a digital modulation scheme such as QAM where data is typically transmitted in symbols of 4 bits or more, the signal's constellation diagram is arranged so that the bit patterns conveyed by adjacent constellation points differ by only one bit.

Regulations limit the bandwidth of a signal transmitted in the HF bands, and the advantages of frequency modulation are greatest if the FM signal is allowed to have a wider bandwidth.

In binary chirp modulation, binary data is transmitted by mapping the bits into chirps of opposite chirp rates.

Modern FDM systems often use sophisticated modulation methods that allow several data signals to be transmitted through each frequency channel.

For some period of time, there had been a continuing lobby for changing the modulation for ATSC to COFDM, the way DVB-T is transmitted in Europe, and ISDB-T in Japan.

AM refers to amplitude modulation, a mode of broadcasting radio waves by varying the amplitude of the carrier signal in response to the amplitude of the signal to be transmitted.

In the last years more advanced modulation formats like phase-shift keying or even orthogonal frequency-division multiplexing have been investigated to counteract effects like dispersion that degrade the quality of the transmitted signal.

FM, or frequency modulation radio is often transmitted on a higher frequency than AM radio.

In these systems, the analog audio signal is digitized, compressed using formats such as mp2, and transmitted using a digital modulation scheme.

Where modulation ( M ) is computed from the following image or light brightness:

Because the MO activity is usually very small, normally less than 1 °, in conventional systems, the monochromator produces quasi-monochromatic light in a narrow wavelength window since the amplitude of modulation is wavelength dependent.

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.

Most microphones today use electromagnetic induction ( dynamic microphone ), capacitance change ( condenser microphone ), piezoelectric generation, or light modulation to produce an electrical voltage signal from mechanical vibration.

L-AAAD activity in rat retinas is modulated by environmental light, and this modulation is associated with dopamine D1 receptors and alpha 2 adrenoceptors.

Sophisticated modulation spectroscopy measurement methods based upon modulating the crystal structure by pressure or by other stresses and observing the related changes in absorption or reflection of light have advanced our knowledge of these materials.

The science of photonics includes the generation, emission, transmission, modulation, signal processing, switching, amplification, and detection / sensing of light.

The science of photonics includes investigation of the emission, transmission, amplification, detection, and modulation of light.

Active methods typically involve using an external signal to induce a modulation of the intra-cavity light.

When driven with an electrical signal, this produces a sinusoidal amplitude modulation of the light in the cavity.

If the modulation rate f is synchronised to the cavity round-trip time τ, then a single pulse of light will bounce back and forth in the cavity.

The actual strength of the modulation does not have to be large ; a modulator that attenuates 1 % of the light when " closed " will mode-lock a laser, since the same part of the light is repeatedly attenuated as it traverses the cavity.

If the frequency of modulation is matched to the round-trip time of the cavity, then some light in the cavity sees repeated up-shifts in frequency, and some repeated down-shifts.

As long as the modulation frequency is kept above the fusion threshold, the perceived intensity can be changed by changing the relative periods of light and darkness.

In addition to increasing with average illumination intensity, the fusion frequency also increases with the extent of modulation ( the maximum relative decrease in light intensity presented ); for each frequency and average illumination, there is a characteristic modulation threshold, below which the flicker cannot be detected, and for each modulation depth and average illumination, there is a characteristic frequency threshold.

The former can be achieved by the use of a modulation technique, whereas the latter can be obtained by placing the gas inside a cavity in which the light passes through the sample several times, thus increasing the interaction length.

In WMS the wavelength of the light is continuously scanned across the absorption profile, and the signal is detected at a harmonic of the modulation frequency.

In FMS, the light is modulated at a much higher frequency but with a lower modulation index.

The modulation may be imposed on the phase, frequency, amplitude, or polarization of the modulated beam.

It differed from VOR primarily in its modulation system, adding a Lorentz-like signal to accurately define the center of the rotating beam.

ILS is essentially a combination of the beam system's narrow fan-shaped broadcasts with a modulation scheme that allows automated display, similar to VOR.

Although Jones had correctly guessed the beam layout ( and acknowledges it was only a guess ), the modulation frequency had been measured incorrectly as 1500 Hz, but was in fact 2000 Hz.

In the moving frame of the electron beam, the velocity modulation is equivalent to a plasma oscillation.

Although initially confused by the Enterprises shield modulation, the Borg lock the vessel in a tractor beam and begin cutting open the hull.

The electromagnetic field due to the RF signal in the RF circuit interacts with the electron beam, causing bunching of the electrons ( an effect called velocity modulation ), and the electromagnetic field due to the beam current then induces more current back into the RF circuit ( i. e. the current builds up and thus is amplified as it passes down ).

A spatial light modulator ( SLM ) is an object that imposes some form of spatially varying modulation on a beam of light.

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.

A rapidly rotating polygonal mirror gives the laser beam the horizontal refresh modulation.

The modulation can be accomplished after the beam is generated.

The brightness of the focused spot is determined by the intensity modulation of the light beam.

This periodic modulation can be probed by a third laser beam, the probe beam.

When the probe beam is propagating through the periodically altered medium, it acquires the same modulation.