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-135 anti-ballistic missile system A-135 anti-ballistic missile system The A-135 (NATO: ABM-3 Gorgon) anti-ballistic missile system is a Russian military complex deployed around Moscow to counter enemy missiles targeting the city or its surrounding areas. It became operational during 1995. It is a successor to the previous A-35, and complies with the 1972 Anti-Ballistic Missile Treaty. The A-135 system attained "alert" (operational) status on February 17, 1995. It is operational although its 51T6 (NATO reporting name: SH-11) component was deactivated in February 2007. A newer missile (PRS-1M) is expected to replace it. There is an operational test version of the system at the test