As proposed by SLAC, the efficiency of a pulse compressor of the SLED-II type could be increased by changing both the phase of the microwave source and the coupling coefficient of the delay line. In the existing SLED-II system at frequency 11.4 GHz, the resonant delay line is coupled with the source via an iris with a constant reflection coefficient. Replacement of the iris with an active component makes it possible to create an active SLED-II system. In this paper, the use of plasma switches as the active elements is discussed. Plasma switches have been developed and tested at a high-power level for production of flattop compressed pulses. Active switching of SLED-II has demonstrated a marked increase in efficiency (by 20%) and power gain (by 37%) as compared with passive switching. The active compressor has produced 173 ns rf flattop output pulses with a power of about 112 MW.