Two-port network
= Two-port network
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A <two-port network> relates voltage and current, or incoming and outgoing travelling-wave amplitudes, at two pairs of electrical terminals. Power-normalized scattering parameters obey $b_i=\sum_jS_{ij}a_j$. In a reciprocal network with equal reference impedances, $S_{12}=S_{21}$. A load reflection at port 2 can return through both transmission coefficients to port 1.