Definition
Zero-Order Hold Sampling -
The samples of a function are represented by piecewise constant function.
In other words, the samples are represented by unit-step functions.
x(t) -> X ----> h(t) -> $ x_0(t) $
^
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p(t) = $ \sum_{n = -\infty}^{\infty}d(t-nT) $
$ \begin{align} h(t) &= {1, when 0 < t < T}\\ &= {0, else }\\ \end{align} $
