A gamma-ray spectrometer in an energy range of 0.3-2000 MeV based on CsI(Tl) single crystals with a total area of 32 x 36 cm(2) and 18 cm thickness is described. A modular structure of the construction allows for logics optimization of the selection of valid events, effective background suppression, and appreciable extension of the operating range of the counting rate of gamma-events. A fast system for stabilizing the energy scale by a pulse light source and a slow stabilization-calibration system with the use of a source of "tagged" gamma-quanta are employed. An energy resolution of 9.9 +/- 0.1% at 0.662 MeV and a time resolution for coincidence and anticoincidence of 0.1 mu s are obtained. The main results of calculating the spectrometer characteristics are presented.

The wide-band specctrometer ''Natalya-2M'' is designed for operating onboard ''PHOTON'' mission for registration of gamma-rays and neutrons from Solar flares. It includes two CsI(Tl) detectors 9 cm thick, placed one above another. The sensitive area of each is 1300 cm(2). The upper detector is surrounded by plastic scintillatior dome. To discriminate gamma and neutron interactions the pulse shape discrimination is used Totally gamma-rays are registered in energy region from 0,2 MeV up to 2000 MeV and neutrons with energy more 10 MeV.Results of calibrations and Monte-Carlo simulations are given. An energy resolution for gamma-rays is 14% (at E=0.662 MeV), 6.0% (10 MeV) and 12% (100 MeV).