  Within the quantum sine-Gordon model a transmission matrix describing the
scattering of a soliton with a fused pair of integrable defects is proposed.
The result is consistent with the classical picture of scattering and
highlights the differences between two defects located at separated points and
two defects fused at the same point. Moreover, the analysis reveals how, for
certain choices of parameters, both the soliton-soliton and the
lightest-breather-soliton S-matrices of the sine-Gordon model are embedded
within the transmission matrix, supporting an interpretation in which defects
may be regarded as soliton constituents.
