Hệ thống hồi tiếp có các khâu lấy mẫu đồng bộ các khâu nối tiếp nhánh thuận có hàm truyền là

\({G}_{k}\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}=\frac{{G}_{1}\left. z \right.{G}_{2}(z)}{1+{G}_{1}\left. z \right.{G}_{2}(z)H\left. z \right.}\)

\({G}_{k}\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}=\frac{G\left. z \right.}{1+G\left. z \right.H\left. z \right.}\)

\({G}_{k}\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}=\frac{G\left. z \right.}{1+G\left. z \right.}\)

\({G}_{k}\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}=\frac{G\left. z \right.}{1+GH\left. z \right.}\)