  We consider the massive Klein-Gordon field on the half line with and without
a Robin boundary potential.The field is coupled at the boundary to a harmonic
oscillator.We solve the system classically and observe the existence of
classical boundary bound states in some regions of the parameter space. The
system is then quantized, the quantum reflection matrix and reflection cross
section are calculated. Resonances and Ramsauer-Townsend effects are observed
in the cross section. The pole structure of the reflection matrix is discussed.
