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I am read a tutorial:

there is example, says the source signal waveform like this.

enter image description here

I can not understand this, because I did not laid eyes on the rectangle shape wave. who can explain to me?

closed as off-topic by Zac67, Ron Trunk, Ron Maupin Sep 29 '18 at 14:52

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  • This question might be better suited on Electrical Engineering. It's off-topic here. – Zac67 Sep 29 '18 at 12:57
  • The crisp angles and straight lines are what signals look like next to the transmitter, by the time the arrive down the cable at the receiver they can be very messy. This is the fundamental that all signalling technologies need to address, and is the reason for all the twisted pairs and other complexities. More belongs, like Zac says, at Electrical Engineering. – jonathanjo Sep 30 '18 at 10:24
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A square waveform represents a digital signal in which the values represented are discrete; e.g. on or off, bright or dim, high or low voltage. Conversely, there is the smoother sine wave of the analog signal which may be more familiar. Analog signals are converted to digital format for processing by computers through a process called sampling, which represents an approximation of the original analog input. Alternatively signals may originate as digital, such as data sent from a computer over the internet.

analog versus digital waveforms

Your example image reflects a digital signal experiencing the introduction of interference (or noise) with corresponding diversion from the original input on the receiving side. One of the fundamental functions of TCP is error detection/recovery which helps to resolve these types of problems with lossy connections.

  • Welcome and thanks for taking part. Might I suggest that the complexities of sampling noise are really not what the questioner is asking about, and perhaps your diagrams are going to therefore be a bit of a misdirection. – jonathanjo Sep 30 '18 at 10:27
  • @jonathanjo Thanks for the feedback. Updated to remove extraneous details about sampling. – user50384 Sep 30 '18 at 15:33
  • Sorry, but the "square wave = digital, sine wave = analog" approach is rather naive. Both type of signals can easily be used the other way around. – Zac67 Sep 30 '18 at 15:33
  • @GxRxP ... I'd say it's really nothing to do with analogue vs digital, it's to do with sending any kind of signal whatsoever down a line and it coming out somewhat degraded. Zac was right in suggesting this should be at electrical engineering. – jonathanjo Sep 30 '18 at 15:49

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