  The M-channel Anderson impurity model (M=1,2) is studied in the Kondo limit
with a finite voltage bias applied to the conduction electron reservoirs. Using
the Non-Crossing Approximation (NCA), we calculate the local spectral
functions, the differential conductance, and susceptibility at non-zero bias
for symmetric as well as asymmetric coupling of the impurity to the leads. We
describe an effective procedure to solve the NCA integral equations which
enables us to reach temperatures far below the Kondo scale. This allows us to
study the scaling regime where the conductance depends on the bias only via a
scaling function. Our results are applicable to both tunnel junctions and to
point contacts. We present a general formula which allows one to go between the
two cases of tunnel junctions and point contacts. Comparison is also made
between the conformal field theory and the NCA conduction electron
self-energies in the two channel case.
