LYCOS RETRIEVER 
Modulation: Signals
built 297 days ago
Modulation refers to the process of encoding digital data into analog signals for transmission. When transferring data over phone lines, for example, a modem modulates the data into audible tones "carried" on frequencies between 0 Hz and 4 KHz. Once the data reaches its intended destination, another modem demodulates the signal back into digital data. Cable TV networks ... use modulation techniques to transfer data. But instead of audible tones, cable has sophisticated digital modulation schemes to greatly increase the amount of data that can be sent.
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The E-Fex Modulator is a new modulation-based effects-processing VST plug-in. It comes with 64 ready-to-use presets. It features true stereo signal chain, input-delay, gate, gain, echo/delay, four types of filters, ring modulation, 10-oscillator chorus, tremolo, and deep auto-panning. Tags: Modulation, E-Fex Modulator Software downloads 2005-06-07
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At the same time, part of the beam is sent through a reference gas--usually the same gas to be sensed--and it ... acquires power modulation at the set of frequencies m*F + n*f. The reference channel uses a second detector and processing electronics to demodulate the signal at 3*F. Low pass filtering yields an error signal proportional to the temperature error. Standard line locking methods are used to drive this signal to zero by adjusting the laser current or temperature. To guarantee that the system is operating correctly, the concentration of gas in the reference path is also measured, using a filter set to n*f, using an odd value for n, and and RMS-DC converter. Only when the reference gas can be detected is a zero value for the error signal meaningful.
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Edwin Armstrong presented his paper: "A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation", which first described FM radio, before the New York section of the Institute of Radio Engineers on November 6, 1935. The paper was published in 1936. [1]
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Modems perform modulation of the analog signal they put out, and demodulation of the signal they receive. They do this by mixing two signals in a digital signal processor and transmitting the analog result to the phone system as the electrical equivalent of sound. Here is a list of the protocols. The Bell protocols were developed by Bell Telephone prior to the government's breakup of that monopoly. The CCITT is an international standards body, which changed it's name later to the ITU (International Telecommunications Union).
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[M]odulation signals are potentially bipolar. That is, the value of the signal can be either greater or less than zero. A signal that drops below zero may seem absurd: how can you have less than no modulation? In fact, the idea makes sense. If, for example, an envelope generator's output is applied to oscillator pitch, you may want the pitch to rise as the envelope rises, or you may want the pitch to fall as the envelope rises. For that reason, the amount sliders in a good modulation matrix will have zero in the middle and let you set either a positive or a negative modulation amount.
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