The automatic exposure relay (X-ray exposure meter) enables the exposure time in roentgenography of diverse human organs to be determined and fixed with a high degree of accuracy, but the subsequent protracted commutation of the main and control circuits of the roentgen-diagnostic apparatus tends to practically bring to naught this high precision. The paper deals with an analysis of commutation delays and lags in different control systems of the roentgen apparatus and with assessing the effect they have on the quality of the X-ray picture.