The problem of normalization of the characteristics of highly sensitive radiation receivers is extremely urgent at this time. On the one hand, this is associated with the rapid growth of demands on the accuracy of measurement and the appearance of new parameters, and on the other, by the absence of appropriate metrological support although the developments in the area mentioned proceed both in the USSR [1] and abroad [2, 3]. A RCD test stand, containing an optical module and a control panel, has been developed to investigate the fundamental parameters and characteristics of radiation detectors subjected to weak thermal fluxes. The optical module consists of three independent components, a calibrated radiation source, a measuring chamber with radiation converter, and the radiation detector being investigated. Depending on the kind of detector and the problem being solved, the possibility is provided for conducting the investigations under normal conditions, in a vacuum, and at helium temperatures. Used as radiation sources are an AChT type vacuum emitter operating in the 300-350 K temperature band with discreetness 10 -2 K of the temperature setting and 5-10-SK error, an AChT type vacuum emitter operating in the 250-300 K temperature band with 5.10 -1 K discreetness of temperature assignment and 5-10 -2 K error of its maintenance, and a SiRSh-10-300 light measuring lamp. The AChT emitters contain a sealed housing, damper, screen, and emitting cavity with not less than 0.997 rate effective emissivity. Temperature radiators and shapers of its increments are paced in the electronics modules. The measuring chamber is a nitrogen--helium cryostat containing emission converter components (modulator, diaphragms, and interchangeable attenuators). Common to all the RCD test stand emission converters is the principle of producing normalized illumination, nonselective emission attenuation by using calibrated diaphragms and interchangeable attenuators, in the plane of the detector sensing element. The interchangeable calibrated converter diaphragms change the illumination within the limits of two orders of magnitude. An SZO attenuator, in which the change in incident beam power is carried out by a change in the angle of aspect of the emission realizable by using plane-spherical reflectors [4], is used to attenuate the emission in a broad spectrum band with 102-108 discreetness. The SZO attenuator in the RCD test stand is located on a base that is fastened to the bottom of the helium chamber, Stages with one plane and three plane-spherical reflectors from sitat with an aluminum coating are placed on this base. Using such an attenuator with a set of interchangeable input diaphragms permits attenuation of the emission 10-10 s times, where the necessary degree of discretization of the attenuation is assured by the quantity of reflectors and the order of extraction of the plane or spherical surfaces on the optical axis. The DIS attenuator used as interchangeable emission converter of the RCD test stand is in the form of a module of four spheres having combined orifices. Each sphere is assembled from two hemispheres fabricated by the method of "extrusion" from sheet duraluminum with subsequent chemical etching to obtain diffusely reflecting surfaces. Spheres of radius R = 5 cm with r = 0.5 cm orifices are installed on the same base as is the SZO attenuator. Each sphere assured attenuation on the order of 102 for the parameters selected. Experiments to investigate the DIS characteristics in the RCD test stand were not performed in the same volume as with the SZO whereupon it does not assure discretization of the attenuation. However, its utilization can turn out to be sufficiently promising in the investigation of the threshold characteristics of highly sensitive radiation detectors, especially matrix.