Sound amplification by stimulated emission of radiation phenomenon, known as the Larsen effect, is the result of a positive feedback. In general, every oscillator consists of three main parts. These are the power source or pump, the amplifier and the positive feedback leading to the output. The corresponding parts in a SASER device are the excitation or pumping mechanism, the active (amplifying) medium, and the feedback leading to acoustic radiation. Pumping can be performed, for instance, with an alternating electric field or with some mechanical vibrations of resonators. The active medium should be a material in which sound amplification can be induced. An example of a feedback
A-235 anti-ballistic missile system eliminates the use within the limited armed conflict and other situations of this kind; secondly, the system must be mobile, without a rigid binding to any object or center; thirdly, it must provide interception at an altitude of at least 500–750 km, that is, at Low Earth Orbit] . A-235 anti-ballistic missile system A-235 PL-19 "Nudol" () is a Russian anti-ballistic missile and anti-satellite weapon system in development. This system is designed to deflect a nuclear attack on Moscow and important industrial regions. The main developer of the system is JSC Concern VKO Almaz-Antey. The new system should replace the