  SOXS is a new spectrograph for the New Technology Telescope (NTT), optimized
for transient and variable objects, covering a wide wavelength range from 350
to 2000 nm. SOXS is equipped with a calibration unit that will be used to
remove the instrument signatures and to provide wavelength calibration to the
data. The calibration unit will employ seven calibration lamps: a
quartz-tungsten-halogen and a deuterium lamp for the flat-field correction, a
ThAr lamp and four pencil-style rare-gas lamps for the wavelength calibration.
The light from the calibration lamps is injected into the spectrograph
mimicking the f/11 input beam of the NTT, by using an integrating sphere and a
custom doublet. The oversized illumination patch covers the length of the
spectrograph slit homogeneously, with $< 1\%$ variation. The optics also
supports the second mode of the unit, the star-simulator mode that emulates a
point source by utilizing a pinhole mask. Switching between the direct
illumination and pinhole modes is performed by a linear stage. A safety
interlock switches off the main power when the lamp box cover is removed,
preventing accidental UV exposure to the service personnel. All power supplies
and control modules are located in an electronic rack at a distance from the
telescope platform. In this presentation we describe the optical, mechanical,
and electrical designs of the SOXS calibration unit, and report the status of
development in which the unit is currently in the test and verification stage.
