# Transmission system

A **transmission system** (often just short *system* ) is in the system theory , a mathematical model of a process that a signal converts and transmits. The signal supplied is called the *input signal* and the resulting converted signal is called the *output signal* . The way in which the signal is converted or how these two signals are related to one another is described by the transfer function.

## Single-size and multi-size systems

A transmission system that has only one input and one output is called a **single- ****variable system** or **SISO system** (from English *single input, single output* )

If the system has several inputs and outputs, one speaks of a **multi-variable system** or *MIMO system* (from English *multiple input, multiple output* ).

The **SIMO systems** (from *single input, multiple output* ) with one input and several outputs still exist as a mixed form . And vice versa, **MISO systems** (from *multiple input, single output* with multiple inputs and only one output).

## Dynamic and static systems

- static: The value of the output signal y (t) depends at any point in time t only on the current value of the input signal u (t). (algebraic description)
- dynamic: The output signal depends on previous input signals. (Description using differential equations)

## Systems with concentrated and distributed parameters

- concentrated parameters: effect arrangements with location-independent signals (description by means of ordinary differential equations)
- distributed parameters: effect arrangements with position-dependent signals (description using partial differential equations)

## Linear and non-linear systems

A system is called linear if the following two conditions are met:

- Reinforcement principle:
- Overlay principle:

If either or both of these conditions are not met, the system is said to be non-linear.

## Time-variable and time-invariant systems

- time-variable: system parameters change over time (e.g. mass of a rocket). Adaptive controllers are necessary to influence such systems.
- time-invariant: systems with constant system parameters.

## Systems with continuous and time-discrete signals

For processing by computers, continuous signals from physical systems are converted into time-discrete signals. This system is called the scanning system.