  Type-I quantum impurities are investigated in the context of the integrable
Heisenberg model. This type of defects is associated to the (q)-harmonic
oscillator algebra. The transmission matrices associated to this particular
type of defects are computed via the Bethe ansatz methodology for the XXX
model, as well as for the critical and non-critical XXZ spin chain. In the
attractive regime of the critical XXZ spin chain the transmission amplitudes
for the breathers are also identified.
