In order to determine the optimal retarding environment for long-term delays of radio frequency (RF) signals, data of the research and development for electric, acoustic-electronic, acoustic-optical, spin, superconducting circuits delay were summarized. It is concluded, that none of the existing classes do not fully meet modern requirements. Comparing technical features (Table 1) have been achieved, showed that in terms of bandwidth and maximum delay time the best option is provided with active electric delay circuit based on a digital radio frequency memory (DRFM), which disadvantages are EMC problems and high power consumption. Evaluations of limiting characteristics for a new approach based on fiber-optic delay circuit clearly show that a single-channel active fiber optic delay circuit (FODC) of RF signals can provide a delay time interval of 3.2 ns to 30 ms in the entire operating band from 50 MHz to 40 GHz.