Some characteristics of detectors of bremsstrahlung and electron radiation of a DBM-I dosimeter which was used for the registration of absorbed doses on a new serial B5M-25 betatron are presented. The dependence of sensitivity of gallium-arsenide detectors upon the maximal energy of bremsstrahlung radiation spectra, rate of the absorbed dose and the temperature of the detector is defined. An assessment of the stability of operation of the dosimeter was made. (auth)