Summarizing over the properties of a function we state 1. a transfer function is defined only for a linear system, and strictly only for time-invariant system 2. A transfer function between an input variable and output variable of a system is defined as the ratio of the Lap lace transform of the output to the input 3. All initial conditions of the system are assumed to zero 4. a transfer function is independent of input excitationSummarizing over the properties of a function we state: 1.A transfer function is defined only for a linear system, and strictly, only for time-invariant system. 2.A transfer function between an input variable and output variable of a system is defined as the ratio of the Lap lace transform of the output to the input. 3.All initial conditions of the system are assumed to zero. 4.A transfer function is independent of input excitation