Systems

In electronics it is frequently easier to break projects down into their smallest components. By doing this we can design the components independent of each other. Then after each component has been fully designed and tested, we can connect all of the components to each other. If every individual component functions, then the final resulting system should function as well.

A good example of this is a microphone amplifier. The end goal is to make an amplifier that has a microphone hooked up to one side, and a loudspeaker connected to the other. Four systems are needed.

1. A microphone
2. A system that knows how to amplify the microphone's signal to a known level.
3. A system that knows how to amplify from the known level to the high level that speakers require.
4. A set of speakers

A microphone to speaker amplifier might look like this.

Notice that there is only one line connecting each small system within the large system. That line is the signal traveling from one block to the next.

Signals

In electronics it is usually easier to talk about voltages like they are signals flowing through systems. It is generally just assumed that GND is 0 volts. So when a signal or voltage of 5 volts is needed, this is in reference to GND.

Signals sometimes carry information, such as voice or data. When this is the case, the signal voltage usually goes up and down very rapidly to represent the information. In the microphone amplifier example earlier, the line connecting each block of the system is carrying voice from the microphone to the speakers. Really what is happening is the voltage on that wire is going up and down very rapidly in response to the voice.