  The construction of type II Backlund transformation for the sine-Gordon and
the Tzitzeica-Bullough-Dodd models are obtained from gauge transformation. An
infinite number of conserved quantities are constructed from the defect
matrices. This guarantees that the introduction of type II defects for these
models does not spoil their integrability. In particular, modified energy and
momentum are derived and compared with those presented in recent literature.
