Translations:Analog linear time-invariant systems/15/en

The impulse-response function represents an important characterization of a linear time-invariant system. The impulse response $h\left(t\right)$ is defined as the output of the system to a Dirac delta function input $\delta \left(t\right)$; that is, $h\left(t\right)=L\left(\delta \left(t\right)\right)$. Because we regard the Dirac delta function as a causal signal, we see that we can distinguish a causal system from a noncausal system by the impulse response. That is, a system is causal if and only if h(t) is one sided (or causal).