Shomer-Tec's countermeasure device against laser surveillance Laser Surveillance Defeater was designed to be effective, inexpensive, compact, and portable. It interrupts, masks, and jams laser demodulation by transmitting human voice frequencies to a window to "drown out" typical conversation. Most laser receivers have a "notch filter" to isolate and enhance human voices; this device was engineered to defeat such filters by centering its frequency output at the middle of the human voice range so that if the notch filter is used, it will also filter out a major portion of the human voice range, making the results useless. The Laser Surveillance Defeater is ideal for government offices, corporate facilities, high-rise buildings, even homes. Completely portable, it installs and un-installs on windows instantly with its integral suction component. Powered by one 9-volt alkaline battery (included), which provides approximately 500 hours of operation. Equipped with on/off switch and bright blue LED power indicator. Deploy one unit per window.