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A time-domain reflectometer; an instrument used to locate the position of faults on lines from the time taken for a reflected wave to return from the discontinuity.. A signal travelling along an electrical transmission line will be partly, or wholly, reflected back in the opposite direction when the travelling signal encounters a discontinuity in the characteristic impedance of the line, or if ...
An emergency locator beacon is a radio beacon, a portable battery powered radio transmitter, used to locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons are carried by aircraft, ships, vehicles, hikers and cross-country skiers. In case of an emergency, such as the ...
The first use of a national emergency telephone number began in the United Kingdom in 1937 using the number 999, which continues to this day. [6] In the United States, the first 911 service was established by the Alabama Telephone Company and the first call was made in Haleyville, Alabama, in 1968 by Alabama Speaker of the House Rankin Fite and answered by U.S. Representative Tom Bevill.
For long delay multipath, the receiver itself can recognize the wayward signal and discard it. To address shorter delay multipath from the signal reflecting off the ground, specialized antennas (e.g., a choke ring antenna) may be used to reduce the signal power as received by the antenna. Short delay reflections are harder to filter out because ...
Direction finding antenna near the city of Lucerne, Switzerland. Direction finding ( DF ), or radio direction finding ( RDF ), is the use of radio waves to determine the direction to a radio source. The source may be a cooperating radio transmitter or may be an inadvertant source, a naturally-occurring radio source, or an illicit or enemy system.
A major revision to the storm signal system took place in 1917 when the new local and non-local storm signal codes were introduced on 1 July. The new local code was the first numbered tropical cyclone signal system in Hong Kong, consisting of seven signals (1 to 7)providing a standby signal, gale signals in four directions (N'ly, S'ly, E'ly and W'ly), an increasing gale signal and a hurricane ...
The process of geolocating a signal requires some knowledge of the signal and all the techniques in order to get an accurate location. The geolocation of a CW signal is nearly impossible with TDOA-FDOA. Nevertheless, a nominally CW transmission can contain imperfections, especially if a station transmits near its maximum EIRP.
The International Code of Signals ( INTERCO) is an international system of signals and codes for use by vessels to communicate important messages regarding safety of navigation and related matters. Signals can be sent by flaghoist, signal lamp ("blinker"), flag semaphore, radiotelegraphy, and radiotelephony. The International Code is the most ...