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Ringdown
In telephony, ringdown is a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp or cause the operation of a self-locking relay known as a ''drop''. Ringdown is used in manual operation, and is distinguished from automatic signaling by dialing a number. The signal consists of a continuous or pulsed alternating current (AC) signal transmitted over the line. It may be used with or without a telephone switchboard. The term originated in magneto telephone signaling in which cranking the magneto generator, either integrated into the telephone set or housed in a connected ringer box, would not only ''ring'' its bell but also cause a drop to fall ''down'' at the telephone exchange switchboard, marked with the number of the line to which the magneto telephone instrument was connected. The last ringdown telephone exchange in the United States was located at Bryant Pond, Maine, had 400+ subscribers, and converted to dial servic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Black Hole
A binary black hole (BBH) is a system consisting of two black holes in close orbit around each other. Like black holes themselves, binary black holes are often divided into stellar binary black holes, formed either as remnants of high-mass binary star systems or by dynamic processes and mutual capture; and binary supermassive black holes, believed to be a result of galactic mergers. For many years, proving the existence of binary black holes was made difficult because of the nature of black holes themselves and the limited means of detection available. However, in the event that a pair of black holes were to merge, an immense amount of energy should be given off as gravitational waves, with distinctive waveforms that can be calculated using general relativity. Therefore, during the late 20th and early 21st century, binary black holes became of great interest scientifically as a potential source of such waves and a means by which gravitational waves could be proven to exist. Bin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone Exchange
telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers. In historical perspective, telecommunication terms have been used with different semantics over time. The term ''telephone exchange'' is often used synonymously with ''central office'', a Bell System term. Often, a ''central office'' is defined as a building used to house the inside plant equipment of potentially several telephone exchanges, each serving a certain geographical area. Such an area has also been referred to as the exchange or exchange area. In North America, a central office location may also be identified as a ''wire center'', designating a facility to which a telephone is connected and obtains dial tone. For business and billing purposes, telecommunication carriers def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Courtesy Phone
A courtesy telephone is a telephone located in airport terminals, large train stations, hotel lobbies, and other places where many travellers are expected, which is used to relay messages to a specific person. It is typically used in connection with a public address system announcement of the style "Gwen Cooper, please pick up the nearest white courtesy telephone." Courtesy telephones may have a distinctive color, which is traditionally white in US airports, and most have no dialing capabilities but rather are simple ringdown stations to reach an operator or other fixed number. Some double as emergency telephones, having buttons by which a user can distinguish between emergency use and inquiry. Customers can use a courtesy phone to seek information, such as where to find further transport or a person trying to meet them. Some courtesy phones provide a direct line to a number of advertised businesses, such as motels or taxis. They may be located near baggage claim, ticketing areas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hotline
A hotline is a point-to-point communications link in which a call is automatically directed to the preselected destination without any additional action by the user when the end instrument goes off-hook. An example would be a phone that automatically connects to emergency services on picking up the receiver. Therefore, dedicated hotline phones do not need a rotary dial or keypad. A hotline can also be called an automatic signaling, ringdown, or off-hook service. For crises and service True hotlines cannot be used to originate calls other than to preselected destinations. However, in common or colloquial usage, a "hotline" often refers to a call center reachable by dialing a standard telephone number, or sometimes the phone numbers themselves. This is especially the case with 24-hour, noncommercial numbers, such as police tip hotlines or suicide crisis hotlines, which are staffed around the clock and thereby give the appearance of real hotlines. Increasingly, however, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-dialable Point
In conventional landline telephony, a non-dialable toll point or toll station was a lone station or line serving a rural subscriber many miles from the nearest central office. As it had no home telephone exchange and therefore no local calling area, all connections were obtained manually from the long distance operator. These toll stations were one of multiple categories of non-dialable points which could only be reached with assistance from the inward operator at destination. Other non-dialable points included locations reachable only by some form of two-way radio and specific categories of manual service. As manual services are replaced by automated infrastructure and satellite telephony now reaches the most distant points on the globe, truly non-dialable points are becoming rare. Toll stations To reach remote rural locations, telephone companies have been created with as little as one subscriber (the Methodist Episcopal Corporation, established in the 1940s to interconnec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Key Telephone Unit
A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX). A business telephone system differs from an installation of several telephones with multiple central office (CO) lines in that the CO lines used are directly controllable in key telephone systems from multiple telephone stations, and that such a system often provides additional features related to call handling. Business telephone systems are often broadly classified into key telephone systems, and private branch exchanges, but many hybrid systems exist. A key telephone system was originally distinguished from a private branch exchange in that it did not require an operator or attendant at the switchboard to establish connections between the central office trunks and stations, or between stations. Technologically, private branch exchanges share lineage with centra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dedicated Line
In computer networks and telecommunications, a dedicated line is a communications cable or other facility dedicated to a specific application, in contrast with a shared resource such as the telephone network or the Internet. It is a communication path between two points. In practice, such services may not be provided by a single, discrete, end-to-end cable, but they do provide guarantees of constant bandwidth availability and near-constant latency, properties that cannot be guaranteed for more public systems. Such properties add a considerable premium to the price charged. As more general-purpose systems have improved, dedicated lines have been steadily replaced by intranets and the public Internet, but they are still useful for time-critical, high-bandwidth applications such as video transmission. Some institutions such as NPR and other news agencies have large numbers of private lines with people that they frequently interview, (often government agencies) though these are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calling Party Control
In telecommunication, supervision is the monitoring of a telecommunication circuit for telephony to convey to an operator, user, or a switching system, information about the operational state of the circuit. The typical operational states of trunks and lines are the idle and busy states, seizure, and disconnect. The states are indicated by various electrical signals and electrical conditions depending on the type of circuit, the type of terminating equipment, and the type of intended service. Answer and disconnect supervision are functions of line signaling that convey circuit seizure and disconnect. Answer supervision indicates that a call has been answered. Disconnect supervision provides a signal that the call has been disconnected. For example, the called party may indicate to the telephone exchange that the call is being disconnected by the called party by allowing loop current to flow in the line, or the called party indicates to the exchange that the call is being answered. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Independent System Operator
A regional transmission organization (RTO) in the United States is an electric power transmission system operator (TSO) that coordinates, controls, and monitors a multi-state electric grid. The transfer of electricity between states is considered interstate commerce, and electric grids spanning multiple states are therefore regulated by the Federal Energy Regulatory Commission (FERC). The voluntary creation of RTOs was initiated by FERC Order No. 2000, issued on December 20, 1999. The purpose of the RTO is to promote economic efficiency, reliability, and non-discriminatory practices while reducing government oversight. An independent system operator (ISO) is similarly an organization formed at the recommendation of FERC. In the areas where an ISO is established, it coordinates, controls, and monitors the operation of the electrical power system, usually within a single US state, but sometimes encompassing multiple states. RTOs typically perform the same functions as ISOs but co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Control Tower
Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organize and expedite the flow of air traffic, and provide information and other support for pilots. Air traffic controllers monitor the location of aircraft in their assigned airspace by radar and communicate with the pilots by radio. To prevent collisions, ATC enforces traffic separation rules, which ensure each aircraft maintains a minimum amount of empty space around it at all times. In many countries, ATC provides services to all private, military, and commercial aircraft operating within its airspace. Depending on the type of flight and the class of airspace, ATC may issue ''instructions'' that pilots are required to obey, or ''advisories'' (known as ''flight infor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Session Initiation Protocol
The Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, and terminating communication sessions that include voice, video and messaging applications. SIP is used in Internet telephony, in private IP telephone systems, as well as mobile phone calling over LTE (VoLTE). The protocol defines the specific format of messages exchanged and the sequence of communications for cooperation of the participants. SIP is a text-based protocol, incorporating many elements of the Hypertext Transfer Protocol (HTTP) and the Simple Mail Transfer Protocol (SMTP). A call established with SIP may consist of multiple media streams, but no separate streams are required for applications, such as text messaging, that exchange data as payload in the SIP message. SIP works in conjunction with several other protocols that specify and carry the session media. Most commonly, media type and parameter negotiation and media setup are performed with the Session Descripti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analog Telephone Adapter
An analog telephone adapter (ATA) is a device for connecting traditional analog telephones, fax machines, and similar customer-premises devices to a digital telephone system or a voice over IP telephony network. An ATA is often built into a small enclosure with an internal or external power adapter, an Ethernet port, one or more foreign exchange station (FXS) telephone ports. Such devices may also have a foreign exchange office (FXO) interface for providing alternative access to traditional landline telephone service. The ATA provides dial tone, Ringing Generator, DC power, caller ID data and other standard telephone line signaling (known collectively as BORSCHT) to the telephone connected to a modular jack. The digital interface of the ATA typically consists of an Ethernet port to connect to an Internet Protocol (IP) network, but may also be a USB port for connecting the device to a personal computer. Using such an ATA, it is possible to connect a conventional telephone to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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