Transposed Tapped Delay Line (TTDL)

$\begin{figure}\centering \input fig/tdl.pstex_t \\ {\LARGE Tapped Delay Line (TDL).} \end{figure}$

$\begin{figure}\centering \input fig/ttdl.pstex_t \\ {\LARGE\emph{Transposed} Tapped Delay Line (TTDL).} \end{figure}$

A flow-graph is transposed (or ``reversed'') by reversing all signal paths.

Branchpoints become sums
Sums become branchpoints
Input/output exchanged
Transfer function identical for SISO systems
Derives from Mason's gain formula
Transposition converts direct-form I, II digital filters to two more direct forms