${\displaystyle \epsilon \left(t\right)={\displaystyle \underset{-\infty }{\overset{t}{\int }}\text{δ}\left(\tau \right)\text{d}\tau }=\{\begin{array}{l}0\text{for}t<0\\ 1\text{for}t>0\end{array}}$, where δ(t) is the unit impulse

SEE: Figure 4b), IEC 60050-103:2009, 103-03-01, and IEC 60027-6.

Note 1 to entry: The value ε(0) of the unit-step function ε(t) may remain undefined or may be defined according to the context.