| 单词 | analog |
| 释义 | analog 1. A continuously present and continuously variable signal. In their native, or original, forms, audio and visual signals are analog. An active audio signal is a stream-oriented, i.e., continuously present, acoustic signal. A visual signal is a stream-oriented optical signal. Audio and visual signals travel in a waveform that can vary continuously and infinitely along two parameters amplitude and frequency. Amplitude refers to signal intensity or signal strength, which manifests as volume in audio signals and brightness in visual signals. Frequency refers to the number of waveforms per second, or cycles per second (cps), known in contemporary terminology as Hertz (Hz). Frequency manifests as pitch, or tone, in audio signals, and as color in image and video signals.All electromagnetic energy travels in continuous waveforms.The portions of the electromagnetic spectrum currently usable for telecommunications include electricity, radio, and infrared light. See also digital, electromagnetic spectrum, and Hz. 2. Pertaining to the representation of data in the form of a continuous signal.Transmission of voice, image, and video information are relatively straightforward as they are analog in their native forms. Appropriate conversions to electrical, radio, and optical energy must be made, of course, and adjustments must be made in terms of amplitude and frequency levels, but the native signals and electromagnetic transmission signals are quite compatible in terms of their common analog nature. In order to accomplish the transmission of these native analog signals, the carrier signal (i.e., information-carrying signal) of the transmission system is modulated (i.e., varied, or changed) in order to create an analog of the original information stream.The transmission of digital computer data over an analog network is quite another matter, as a fundamental conversion in signal format must be made through a modem. To accomplish this conversion over an electrified analog network, the ones (1s) and zeroes (0s) of the digital bit stream must be translated into amplitude and frequency variations of the carrier signal. The electromagnetic sinusoidal waveform, or sine wave, can be varied in amplitude at a fixed frequency, using Amplitude Modulation (AM). Alternatively, the frequency of the sine wave can be varied at constant amplitude, using Frequency Modulation (FM). Additionally, both frequency and amplitude can be modulated simultaneously. Finally, the position of the sine wave can be manipulated (actually, can appear to be manipulated), adding the third technique of Phase Modulation, also known as Phase Shift Keying (PSK). See also carrier, digital, and modem. 3. Something that is continuously present and continuously variable. For example, the shadow cast by the gnomon on the flat plate of a sundial is continuously present and continuously variable, at least during the daylight hours. Similarly, the hands of an analog clock, watch, or fuel gauge are continuously present and continuously variable, or essentially so. 4. Something that is analogous to or similar to something else.The electrical waveform of a voice transmission over an analog network is |
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