This makes it harder for the receiving circuit to accurately identify the transitions and clock the incoming signal. Depending on the characteristic impedance of the cable, the capacitance of the cable, and the impedance match between the source and load devices, the corners of the square wave will round off to a greater or lesser degree, and the "flat" portions of the wave will become uneven as well. This means that while the signal may originate as a square wave, it never quite arrives as one. But while the alteration of an analog waveform is progressive and continuous-the more noise is introduced, the more noise will come out of our speaker along with the tone-the digital signal suffers alteration quite differently.įirst, a digital signal, because of its sharp transitions, is highly subject to degradation in its waveform those sharp transitions are equivalent to a long-indeed, an infinite-series of harmonics of the base frequency, and the higher the frequency of the signal, the more transmission line effects, such as the characteristic impedance of the cable, and resulting signal reflections ("return loss") come into play. Both are electrical signals, carried by a stream of electrons in a wire, and so both are subject to alteration by the electrical characteristics of the cable and by the intrusion of outside electrical noise. One of the interesting distinctions between digital and analog signals is that they degrade in rather different ways. Ideally, these transitions are instantaneous, creating what we call a "square wave." This is so despite the fact that, when the signal is decoded, the result may be the very same 1000 Hertz tone, with its continuous slopes and lack of sharp transitions, represented by the analog signal described above.
#LOOPBACK CABLE ANALOG DEVICES SERIES#
Instead, it consists of a series of "1" and "0" bits, encoded according to some particular standard, and delivered as a series of rapid transitions in voltage. If we could use that electrical signal to drive a speaker cone to physically move in and out in that same pattern, we'd hear the tone come out of the speaker.Ī digital signal, unlike an analog signal, bears no superficial resemblance to the information it seeks to convey. If the information is a 1000 Hertz sine-wave tone, for example, the analog signal is a voltage varying from positive to negative and back again, 1000 times per second, in a sine-wave-shaped pattern.
An analog signal represents the information it is intended to convey by presenting a continuous waveform analogous to the information itself. The first generation of video and audio cables were designed with analog signals in mind. To begin that discussion, let's first talk about what digital and analog signals are, and how they perform in cables. Many of the best video cables on the market today were designed primarily for use in the digital domain but can a digital cable really perform well as an analog cable? Can an analog cable be used as a digital cable? What's the difference, anyway, between digital and analog cables? They both move electrons, don't they? All of these are interesting questions, and bear some discussion.
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