  Type II integrable defects with more than one degree of freedom at the defect
are investigated. A condition on the form of the Lagrangian for such defects is
found which ensures the existence of a conserved momentum in the presence of
the defect. In addition it is shown that for any Lagrangian satisfying this
condition, the defect equations of motion, when taken to hold everywhere, can
be extended to give a B\"{a}cklund transformation between the bulk theories on
either side of the defect. This strongly suggests that such systems are
integrable. Momentum conserving defects and B\"{a}cklund transformations for
affine Toda field theories based on the $A_n$, $B_n$, $C_n$ and $D_n$ series of
Lie algebras are found. The defect associated with the $D_4$ affine Toda field
theory is examined in more detail. In particular classical time delays for
solitons passing through the defect are calculated.
