single-frequency device
51Acousto-optics — is a branch of physics that studies the interactions between sound waves and light waves, especially the diffraction of laser light by ultrasound or sound in general.IntroductionOptics has had a very long and full history, from ancient Greece,… …
52Second — This article is about the unit of time. For other uses, see Second (disambiguation). A light flashing approximately once per second. The second (SI unit symbol: s; informal abbreviation: sec) is a unit of measurement of time, and is the… …
53Microchip implant (animal) — For use in humans, see Microchip implant (human). Microchip implant in a cat. A microchip implant is an identifying integrated circuit placed under the skin of a dog, cat, horse, parrot or other animal. The chips are about the size of a large… …
54D-STAR — This article is about the digital voice mode used in amateur radio. For the physical quantity, see Specific detectivity. For the concept in robotics, see D* search algorithm. For more details on this topic, see List of amateur radio modes. ICOM… …
55Intermodulation — A frequency spectrum plot showing intermodulation between two injected signals at 270 and 275 MHz (the large spikes). Visible intermodulation products are seen as small spurs at 280 MHz and 265 MHz. Intermodulation or intermodulation distortion… …
56Digital Audio Broadcasting — For other digital audio broadcasting systems, see Digital radio.   Countries with regular services …
57Auditory brainstem response — The auditory brainstem response (ABR) is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp. The resulting recording is a series of vertex positive waves of which I …
58Telephone exchange — A telephone operator manually connecting calls with cord pairs at a telephone switchboard. In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls. A central… …
59Walkie-talkie — A walkie talkie (more formally known as a handheld transceiver) is a hand held, portable, two way radio transceiver. Originally developed for the Canadian government during the Second World War by Canadian Donald L. Hings, similar designs were… …
60Polarization — ( Brit. polarisation) is a property of waves that describes the orientation of their oscillations. For transverse waves, it describes the orientation of the oscillations in the plane perpendicular to the wave s direction of travel. Longitudinal… …
