Interesting Fact

Today, as I was reading about "signals" I constantly kept coming across the term analog signal and discrete signal and digital signal. And I couldn't connect with those terms .. As usual. So I started wondering why is an analog signal called analog? Where did the term discrete come from. And out came the dictionary!

Analog signal : The US version of "Analogue" it simply means analogous ie similar to something else. An analog signal is simply a signal ( ie a symbol) which is exactly similar to another quantity, the quantity that it is modeling. Thats why is analog.

Discrete : The word discrete comes from the latin word discerner ie dis + cernere (to separate) meaning to divide. Discrete would then describe an object that has separate parts or form. Which I guess would rightly describe a run-off-the-mill discrete signal.

Digital signal : I guess most of us would be aware, digit means toe or finger. I think the name digital signal is simply a reflection of the fact that there are finite number of levels in a digital signal, mostly two of course, like the finite number of fingers.

And the way I understand it, continuous and discrete, do not describe the range of values or the kind of values the signal can take, rather, the time axis or the number of values that are taken by the system or the way the signal is sampled basically.

Analog and digital, on the other hand describe the values of the signal. So does the term quantized. An continuous-time system can be quantized and so can a discrete-time system.

You can either measure the signal continuously for ten minutes to get a continuous signal or measure for 1 second every one minute, ten times to get a discrete signal. That'ss the difference. But when you measure, if the signal takes any value, then its analog, or if it takes only specific steps of values, its quantized, and if it only takes a specified set of values, its digital.

So this was today's interesting fact.
Till next time.