  We calculate the expected effects on the spectral energy distributions and
light curves in X-ray binary jets from eclipses by the donor stars. Jets will
be eclipsed for all inclination angles, with just the height along the jet
where the eclipse takes place being set by the orbital parameters. Typically,
eclipses will lead to 5-10\% reductions in the jet emission over a range of a
factor of few in wavelength with a periodic modulation. In ideal systems with
high inclination angles, relatively even mass ratios, and modest jet speeds,
the eclipses may be deeper. We discuss how eclipses can be used to measure
binary system parameters, as well as the height of the bases of the jets. We
also discuss how, with data sets that will likely require future facilities,
more detailed tests of models of jet physics could be made, by establishing
deviations from the standard recipes for compact conical flat spectrum jets,
and by determining the ingress and egress durations of the eclipses and
measuring the transverse size of the jets. We provide representative
calculations of expectations for different classes of systems, demonstrating
that the most promising target for showing this effect in the radio band are
the longer period "atoll"-class neutron star X-ray binaries, while in the
optical and infrared bands, the best candidates are likely to be the most
edge-on black hole X-ray binaries. We also discuss the effects of the outer
accretion disc eclipsing the inner jet.
