What are digital and analog signals?

[Carlos1010]

Hi all,

So I have a test on this next week and I have no clue what they are, I just want to tell you that i've went on videos and wiki but I still dont understand anything. (Science if not my type) So I have a couple questions on this and there will come much more along the way.

 

1. When are these signals used?

 

2. What are these signals and what devices are using them? 

[ARikozuM]

Think of digital as 1's and 0's.

Think of analog as a wave or pattern of electrical energy.

 

Nearly all devices rely on analog but use digital for the safe(r) transmission of data across wires. Digital music, for example, uses digital to the speakers which will convert the signal back to analog and use that.

[Carlos1010]

4 minutes ago, ARikozuM said:

Think of digital as 1's and 0's.

Think of analog as a wave or pattern of electrical energy.

 

Nearly all devices rely on analog but use digital for the safe(r) transmission of data across wires. Digital music, for example, uses digital to the speakers which will convert the signal back to analog and use that.

So is like digital waves the thing that goes through the wires and circuit board of your device? Is everything with a circuit board a thing that runs on digital signal? Do sound waves go on analog signal? 

[ARikozuM]

1 minute ago, Carlos1010 said:

So is like digital waves the thing that goes through the wires and circuit board of your device? Is everything with a circuit board a thing that runs on digital signal? Do sound waves go on analog signal? 

Sound is analog which is why we can hear it otherwise it would be off (0) or on (1).

[Carlos1010]

3 minutes ago, wrathoftheturkey said:

Wayl technically it could be on or off at every frequency but that would require an infinite number of bits, which would be impossible to measure or detect cuz, you know, infinity

But why do we even have analog systems, why cant we just have digital, is there an advantage of having a analog system? If a PC would be analog what would it look like then because it has to be digital to process something. 

[kirashi]

1 hour ago, Carlos1010 said:

But why do we even have analog systems, why cant we just have digital, is there an advantage of having a analog system? If a PC would be analog what would it look like then because it has to be digital to process something. 

If we had no analogue signals, devices could not output sound. Sound is and always will be analogue, at least until we have digital brain implants.

[skywake]

Basically an analogue signal is raw data. When you take a photo on film, record audio on a tape or send audio down a speaker wire? What you get can't really be defined by a specific number. If that makes sense. For example that photo you take on film? There aren't really "pixels" or specific amounts of Red, Green and Blue. Even before talking about compression or noise a photo on film can have colour values in the areas between "pixels". It can also have an infinite range of colours between defined colours.

 

A digital signal on the other hand is discrete. If you have a 500x500 pixel image with 256 colours (as a simple example) you can't have a colour value somewhere between the defined range of colours in a position between pixels. It's one of those 256 colours in one of those positions on that 500x500 pixel grid. Obviously with improved bandwidth, sensors and storage? It becomes less of a disadvantage as it would be in that extreme example. But the principle is the same.

 

So as another example. Audio on an audio CD is uncompressed but it's digital. And from the spec we know that it has 2 channels of 16bit signed audio with a sample rate of 44.1khz. Which means that 44.1 thousand times per second an audio CD has a value for the amplitude of the audio signal at that point. It then gives that signal a value for each of the two channels between -32768 and +32767. There is nothing defined outside of those parameters. You can't have a value of 5067.787934 at a point 2/3rds of the way between two samples.

[Carlos1010]

11 minutes ago, skywake said:

Basically an analogue signal is raw data. When you take a photo on film, record audio on a tape or send audio down a speaker wire? What you get can't really be defined by a specific number. If that makes sense. For example that photo you take on film? There aren't really "pixels" or specific amounts of Red, Green and Blue. Even before talking about compression or noise a photo on film can have colour values in the areas between "pixels". It can also have an infinite range of colours between defined colours.

I don't understand this part, is there possible another example you can give me? I understand the digital part thanks very much for that! 

[skywake]

57 minutes ago, Carlos1010 said:

I don't understand this part, is there possible another example you can give me? I understand the digital part thanks very much for that! 

I'll put it another way. Think of your keyboard and the fact that it has a whole bunch of keys. Each key can be either pressed or not there's no middle ground. There's also no key that's half-way between defined keys. It's either one of the keys on the keyboard or it's not. Because it's entirely digital. Compare that to writing with a pen. You can write with different levels of pen pressure, you can write characters that are a bit between two other characters. They keys on a keyboard are a good enough description of what you can do writing with a pen. But there are things you can do writing with a pen that are "between" the keys.

 

Of course you could invent a larger keyboard with more keys. More secondary functions and so on. Different languages and symbols etc. But there will always be a way to be "between" two key presses with a pen. Because a pen is analogue

[Emmien]

8 hours ago, Carlos1010 said:

So is like digital waves the thing that goes through the wires and circuit board of your device? Is everything with a circuit board a thing that runs on digital signal? Do sound waves go on analog signal? 

Both digital and analogue signals can pass through a circuit board or device.

 

Radios, torches, motorised stuff all carries analogue signals.

 

Calculators, computers, phones, printers and things like that, are digital, with small amounts of analogue.

[Adyn]

Think waves on a beach while you have peaks and troughs they are different heights and depths, that’s analogue. Anything with waves is analogue so think sound, electricity etc.

 

The problem with waves is they are not static so if you were using electricity for a control and you wanted to sample for a certain voltage to use for controls you would get multiple readings at random when you wanted a single value.

 

Hence the requirement for digital so you can have control this is achieved by using a transistor to measure a voltage over a period (think as small as you can) to determine if that signal is a 1 or 0.

 

So now that you have a defined digital signal you can use that to carry out calculations store data whatever you can think of.

 

Now this is the bit audiophiles do not like you can reverse this process to get an analogue output but it is always a representation of the original source. Now you can do things to decrease the sampling time to get a more authentic signal but if a digital process is used anywhere then that becomes a representation of the orginal.