Terminology
Signals

In control theory are important information. Bearer of information is the signal sources are transmitters, receivers provide reception. The signals are divided according to the relationship to self or dependent variable. Independent variable is time and the dependent variable is the amplitude. Distribution of signals is as follows:

- Signals are continuous in time (at each point in time is known amplitude value):
  - Analog signals, the example in Figure 2.3
  - Quantized signals, the example in Figure 2.3
- Signals discontinuous in time (between samples is not known amplitude value):
  - Sampled (discrete) signals, the example in Figure 2.3
  - Amplitude and time-discrete (digital) signals, the example in Figure 2.3

Fig. 2.3: Analog, quantized, sampled, amplitude nonsmooth signal