  The results of the extended quadrahedral NaI(Tl) spectrometer`s calibration
by cosmic muons are presented. The signal amplitude and energy resolution of
the spectrometer have complex dependencies on the voltage at the
photomultiplier and the entry point of the particle into the spectrometer in
the transverse direction. When the voltage across the photomultiplier divider
photomultiplier is U = 1150 V the homogeneous signals area is observed at about
90% of the spectrometer length, the energy resolution is about 7%.
