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Local Access Alert
The Local Access Alert (also known as Local Access System or Emergency Override System) is a warning system designed to warn radio, television stations, cable television broadcast feeds or satellite signals of impending dangers, such as tornadoes, flash flooding and other civil emergencies. The system was largely replaced by the Emergency Alert System in the United States, although it still exists in some areas which have not yet been upgraded, and is still used from time to time in areas that have upgraded to the EAS. The Local Access Alert was used by local law enforcement agencies and emergency management staff, and it's much like the antiquated Emergency Broadcast System. A public servant would dial up a number and PIN through a phone to take control of a certain cable city or cluster in the path of danger. Once the number and PIN are entered, it switches all cable subscribers, regardless of what channel they're on, to a black screen or static and uses a distinct attention si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emergency Population Warning
An emergency population warning is a method whereby local, regional, or national authorities can contact members of the public en masse to warn them of an impending emergency. These warnings may be necessary for a number of reasons, including: * weather emergencies such as tornadoes, hurricanes, and ice storms; * geological disasters such as earthquakes, landslides, volcanic eruptions, and tsunamis; * industrial disasters such as the release of toxic gas or contamination of river water; * radiological disasters such as a nuclear plant disaster; * medical emergencies such as an outbreak of a fast-moving infectious disease; * warfare or acts of terrorism. Many local areas use emergency population warnings to advise of prison escapes, abducted children, emergency telephone number outages, and other events. Requirements In order to develop an effective emergency warning system, certain things are required: * an agreement as to what constitutes an emergency in the area served by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise (video)
Noise, commonly known as static, white noise, static noise, or snow, in analog video and television, is a random dot pixel pattern of static displayed when no transmission signal is obtained by the antenna receiver of television sets and other display devices. Description The random pixel pattern is superimposed on the picture or the television screen, being visible as a random flicker of "dots", "snow" or "fuzzy zig-zags" in some television sets, is the result of electronic noise and radiated electromagnetic noise accidentally picked up by the antenna like air or cable. This effect is most commonly seen with analog TV sets, blank VHS tapes, or other display devices. There are many sources of electromagnetic noise which cause the characteristic display patterns of static. Atmospheric sources of noise are the most ubiquitous, and include electromagnetic signals prompted by cosmic microwave background radiation In Big Bang cosmology the cosmic microwave background (CMB, CMB ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disaster Preparedness In The United States
A disaster is a serious problem occurring over a short or long period of time that causes widespread human, material, economic or environmental loss which exceeds the ability of the affected community or society to cope using its own resources. Disasters are routinely divided into either "natural disasters" caused by natural hazards or "human-instigated disasters" caused from anthropogenic hazards. However, in modern times, the divide between natural, human-made and human-accelerated disasters is difficult to draw. Examples of natural hazards include avalanches, flooding, cold waves and heat waves, droughts, earthquakes, cyclones, landslides, lightning, tsunamis, volcanic activity, wildfires, and winter precipitation. Examples of anthropogenic hazards include criminality, civil disorder, terrorism, war, industrial hazards, engineering hazards, power outages, fire, hazards caused by transportation, and environmental hazards. Developing countries suffer the greatest costs whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Civil Defense
United States civil defense refers to the use of civil defense in the history of the United States, which is the organized non-military effort to prepare Americans for military attack and similarly disastrous events. Late in the 20th century, the term and practice of civil defense fell into disuse. Emergency management and homeland security replaced them. History Pre–World War There is little known history of civil defense in the United States before the twentieth century. Since ancient times, cities typically built walls and moats to protect from invasion and commissioned patrols and watches to keep an eye out for danger, but such activities have not traditionally been encompassed by the term "civil defense." The U.S. has a particular lack of early civil defense efforts because it was seldom threatened with a significant attack. Nonetheless, there are some early examples of what would today be considered civil defense. For example, as early as 1692, the village of Bedfor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Specific Area Message Encoding
Specific Area Message Encoding (SAME) is a protocol used for framing and classification of broadcast emergency warning messages. It was developed by the United States National Weather Service for use on its NOAA Weather Radio (NWR) network, and was later adopted by the Federal Communications Commission for the Emergency Alert System, then subsequently by Environment Canada for use on its Weatheradio Canada service. It is also used to set off receivers in Mexico City and surrounding areas as part of the Mexican Seismic Alert System (SASMEX). History From the 1960s to the 1980s, a special feature of the NOAA Weather Radio (NWR) system was the transmission of a single attention tone prior to the broadcast of any message alerting the general public of significant weather events. This became known as the Warning Alarm Tone (WAT). Although it served NWR well, there were many drawbacks. Without staff at media facilities to manually evaluate the need to rebroadcast an NWR message using ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Cable
Digital cable is the distribution of cable television using digital data and video compression. The technology was first developed by General Instrument. By 2000, most cable companies offered digital features, eventually replacing their previous analog-based cable by the mid 2010s. During the late 2000s, broadcast television converted to the digital HDTV standard, which was incompatible with existing analog cable systems. In addition to providing high-definition video, digital cable systems provide more services such as pay-per-view programming, cable internet access and cable telephone services. Most digital cable signals are encrypted, which reduced the incidence of cable television piracy which occurred in analog systems. History In 1990, General Instrument (acquired by Motorola and now owned by ARRIS Group) demonstrated that it was possible to use digital compression to deliver high quality HDTV in a standard 6 MHz television channel. Using the same technology General ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dial Tone
A dial tone is a telephony Signaling (telecommunication), signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected. It indicates that the exchange is working and is ready to initiate a telephone call. The tone stops when the first dialed digit is recognized. If no digits are forthcoming, the permanent signal, partial dial procedure is invoked, often eliciting a special information tone and an intercept message, followed by the off-hook tone, requiring the caller to hang up and redial. History Early telephone exchanges signaled the switchboard operator when a subscriber picked up the telephone handset to make a call. The operator answered requesting the destination of the call. When manual exchanges were replaced with automated switching systems, the exchange generated a tone to the caller when the telephone set was picked up, indicating that the system was ready to accept dialed digi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Off-hook Tone
The off-hook tone (also off-hook warning, howling tone, or howler tone) is a telephony signal for alerting a user that the telephone has been left off-hook without use for an extended period, effectively disabling the telephone line. North America The off-hook tone in exchanges of the North American Numbering Plan consists of a superposition of tones with the frequencies 1400 Hz, 2060 Hz, 2450 Hz, and 2600 hertz, played at a cadence of on and off. Section 17.2.8 ''Receiver-Off-Hook (ROH) Tone'' The signal is applied to the local loop by the switching system for |
Dual-tone Multi-frequency Signaling
Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. DTMF was first developed in the Bell System in the United States, and became known under the trademark Touch-Tone for use in push-button telephones supplied to telephone customers, starting in 1963. DTMF is standardized as ITU-T Recommendation Q.23. It is also known in the UK as ''MF4''. The Touch-Tone system using a telephone keypad gradually replaced the use of rotary dial and has become the industry standard for landline and mobile service. Other multi-frequency systems are used for internal signaling within the telephone network. Multifrequency signaling Before the development of DTMF, telephone numbers were dialed by users with a loop-disconnect (LD) signaling, more commonly known as pulse dialing (dial pulse, DP) in the United States. It functions by int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siren (alarm)
A siren is a loud noise-making device. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks. Sirens are used on emergency service vehicles such as ambulances, police cars, and fire engines. There are two general types: mechanical and electronic. Many fire sirens (used for calling the volunteer fire fighters) serve double duty as tornado or civil defense sirens, alerting an entire community of impending danger. Most fire sirens are either mounted on the roof of a fire station or on a pole next to the fire station. Fire sirens can also be mounted on or near government buildings, on tall structures such as water towers, as well as in systems where several sirens are distributed around a town for better sound coverage. Most fire sirens are single tone and mechanically driven by electric motors with a rotor attached to the shaft. Some newer sirens are electronically driven speakers. Fire sirens are often called "fire whistles", "fir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morse Code
Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of the inventors of the telegraph. International Morse code encodes the 26 basic Latin letters through , one accented Latin letter (), the Arabic numerals, and a small set of punctuation and procedural signals ( prosigns). There is no distinction between upper and lower case letters. Each Morse code symbol is formed by a sequence of ''dits'' and ''dahs''. The ''dit'' duration is the basic unit of time measurement in Morse code transmission. The duration of a ''dah'' is three times the duration of a ''dit''. Each ''dit'' or ''dah'' within an encoded character is followed by a period of signal absence, called a ''space'', equal to the ''dit'' duration. The letters of a word are separated by a space of duration equal to three ''dits'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone
A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from el, τῆλε (''tēle'', ''far'') and φωνή (''phōnē'', ''voice''), together meaning ''distant voice''. A common short form of the term is ''phone'', which came into use early in the telephone's history. In 1876, Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice at a second device. This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households. The essential elements of a telephone are a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
