Professor Sampler’s Notes: Signal

Topics Covered:

  • Definition of a signal
  • Electrons as signals

One can never step into the same river twice – Heraclitus

A signal is an attempt by human beings to communicate with one another. If one person throws a ball to another person, that ball can be said to be a signal. The Iliad can be one large complex signal or a group of smaller signals (letters, words, etc). Signals are nothing more than information, or messages.

A key property of all signals is that they never stay the same. By the time the second person catches the ball, the ball has already changed. It might seem funny, but things are always in motion. In the example of the ball, one might believe that such a property is of no practical importance, but when the signals are transmitted electronically (instead of balls we throw electrons!), we are dealing with particles and their quantum nature, and this problem takes on very significant proportions.

This property is also the greatest disadvantage in our attempts to preserve analogue signals over longer periods of time. To save something forever is a struggle against the universe.

One of the first signals you’ve probably seen

However, one cool consequence of the above property is that since signals are constantly changing, one can ‘map’ them in time and space. If we define a certain property of a signal, like a color in a signal of moving images, then we can plot a graph to determine every time that color is displayed, or how many of those colors are present, in any given moment, etc. We are only limited by our creativity here.

All we have to do is find a reliable property that can be measured, and then plot its value against time (or even another property) to get a visual representation of how it changes. As you will see later on, time isn’t always a reliable property to measure against. To some, this is a frustrating thing. To others, it is an exciting challenge.

Humans have managed to tame these signals for communication (transmission):
1. Electromagnetic waves
2. Sound waves
3. Electrons

Electromagnetic waves include light, microwaves, radiowaves, infrared waves, ultra-violet waves, you name it. Sound waves include the audible spectrum (what we can hear), ultrasonic waves, etc.

What about electrons? Why are they on the list? For now, just be content knowing Electrons are fast, and when inside conductors and semiconductors they transform from random geeks to superheroes. Even our brains are wired this way. We are continually discovering new things about electrons. In the science of communication, electrons have had a head start, and they haven’t let us down yet.

One question to ponder over: Are electrons waves too?

What signals are being given out here?

Takeaways:

  • A signal is nothing but a message or object human beings use to communicate with each other

Links for further study:

Next: Professor Sampler’s Notes: Waves
Previous: Professor Sampler’s Notes: Analog