standard frequency and time signals
31International Atomic Time — ( [http://www.bipm.org/en/scientific/tai/tai.html TAI] , from the French name Temps Atomique International) is a high precision atomic time standard that tracks proper time on Earth s geoid. It is the principal realisation of Terrestrial Time,… …
32Low frequency — or LF refers to Radio Frequencies (RF) in the range of 30 kHz ndash;300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcast service. In the western hemisphere, its main use is for aircraft… …
33Copper wire and cable — Copper has been used in electric wiring since the invention of the electromagnet and the telegraph in the 1820s.[1][2] The invention of the telephone in 1876 proved to be another early boon for copper wire.[3] Today, despite competition from… …
34Short-time Fourier transform — The short time Fourier transform (STFT), or alternatively short term Fourier transform, is a Fourier related transform used to determine the sinusoidal frequency and phase content of local sections of a signal as it changes over time. STFT… …
35Philippine Atmospheric, Geophysical and Astronomical Services Administration — Pangasiwaan ng Palingkurang Atmosperiko, Heopisikal at Astronomiko ng Pilipinas Agency overview Formed …
36roads and highways — ▪ transportation Introduction traveled way on which people, animals, or wheeled vehicles move. In modern usage the term road describes a rural, lesser traveled way, while the word street denotes an urban roadway. Highway refers to a major… …
37Mobile phone radiation and health — A man speaking on a mobile telephone The effect of mobile phone radiation on human health is the subject of recent interest and study, as a result of the enormous increase in mobile phone usage throughout the world (as of June 2009 …
38Marine mammals and sonar — A Humpback whale Active sonar, the transmission equipment used on some ships to assist with navigation, has been suggested[1] to be detrimental to the health and livelihood of some marine animals, although the precise mechanisms for this are not… …
39rocket and missile system — ▪ weapons system Introduction any of a variety of weapons systems that deliver explosive warheads to their targets by means of rocket propulsion. Rocket is a general term used broadly to describe a variety of jet propelled missiles… …
40Extremely low frequency — (ELF) is the band of radio frequencies from 3 to 30 Hz. ELF was used by the US Navy and Soviet/Russian Navy to communicate with submerged submarines.ExplanationBecause of the electrical conductivity of salt water, submarines are shielded from… …
