On- and Off-hook
In telephony, on-hook and off-hook refer to the two possible states of a receiver. Off-hook referred to the condition that prevailed when telephones had a separate earpiece, which hung from its switchhook until the user wished to activate it; the weight of the receiver no longer depresses the spring-loaded switchhook, thereby connecting the instrument to the telephone line. The term off-hook has the following meanings: The condition that exists when a telephone or other user instrument is in use, i.e. during dialing or communicating. A general description of one of two possible signaling states at an interface between telecommunications systems, such as tone or no tone and ground connection versus battery connection. Note that if off-hook pertains to one state, on-hook pertains to the other; the active state An operating state of a communications link in which data transmission is enabled either for voice or data communications or network signaling. On an ordinary two-wire telephone line, off-hook status is communicated to the telephone exchange by a resistance short across the pair.
When an off-hook condition persists without dialing, for example because the handset has fallen off or the cable has been flooded, it is treated as a permanent loop or permanent signal. The act of going off-hook is referred to as seizing the line or channel; the term on-hook has the following meanings: The condition that exists when a telephone or other user instrument is not in use, i.e. when idle waiting for a call. Note: on-hook referred to the storage of an idle telephone receiver, i.e. separate earpiece, on a switchhook. The weight of the receiver depresses the spring-loaded switchhook thereby disconnecting the idle instrument from the telephone line. One of two possible signaling states, such as tone or no tone, or ground connection versus battery connection. Note: if on-hook pertains to one state, off-hook pertains to the other; the idle state, i.e. an open loop of a subscriber PBX user loop. An operating state of a telecommunication circuit in which transmission is disabled and a high impedance, or "open circuit", is presented to the link by the end instrument.
Note: during the on-hook condition, the link is responsive to ringing signals. The act of going on-hook is referred to as releasing the line or channel, may initiate the process of clearing. Disconnect supervision Hook flash Line signaling Off-hook tone This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C"
A telephone number is a sequence of digits assigned to a fixed-line telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network or other public and private networks. A telephone number serves as an address for switching telephone calls using a system of destination code routing. Telephone numbers are entered or dialed by a calling party on the originating telephone set, which transmits the sequence of digits in the process of signaling to a telephone exchange; the exchange completes the call either to another locally connected subscriber or via the PSTN to the called party. Telephone numbers are assigned within the framework of a national or regional telephone numbering plan to subscribers by telephone service operators, which may be commercial entities, state-controlled administrations, or other telecommunication industry associations.
Telephone numbers were first used in 1879 in Lowell, when they replaced the request for subscriber names by callers connecting to the switchboard operator. Over the course of telephone history, telephone numbers had various lengths and formats, included most letters of the alphabet in leading positions when telephone exchange names were in common use until the 1960s. Telephone numbers are dialed in conjunction with other signaling code sequences, such as vertical service codes, to invoke special telephone service features; when telephone numbers were first used they were short, from one to three digits, were communicated orally to a switchboard operator when initiating a call. As telephone systems have grown and interconnected to encompass worldwide communication, telephone numbers have become longer. In addition to telephones, they have been used to access other devices, such as computer modems and fax machines. With landlines and pagers falling out of use in favor of all-digital always-connected broadband Internet and mobile phones, telephone numbers are now used by data-only cellular devices, such as some tablet computers, digital televisions, video game controllers, mobile hotspots, on which it is not possible to make or accept a call.
The number contains the information necessary to identify uniquely the intended endpoint for the telephone call. Each such endpoint must have a unique number within the public switched telephone network. Most countries use fixed-length numbers and therefore the number of endpoints determines the necessary length of the telephone number, it is possible for each subscriber to have a set of shorter numbers for the endpoints most used. These "shorthand" or "speed calling" numbers are automatically translated to unique telephone numbers before the call can be connected; some special services have their own short numbers The dialing plan in some areas permits dialing numbers in the local calling area without using area code or city code prefixes. For example, a telephone number in North America consists of a three-digit area code, a three-digit central office code, four digits for the line number. If the area has no area code overlays or if the provider allows it, seven-digit dialing may be permissible for calls within the area, but some areas have implemented mandatory ten-digit dialing.
Other special phone numbers are used for high-capacity numbers with several telephone circuits a request line to a radio station where dozens or hundreds of callers may be trying to call in at once, such as for a contest. For each large metro area, all of these lines will share the same prefix, the last digits corresponding to the station's frequency, callsign, or moniker. In the international telephone network, the format of telephone numbers is standardized by ITU-T recommendation E.164. This code specifies that the entire number should be 15 digits or shorter, begin with a country prefix. For most countries, this is followed by an area code or city code and the subscriber number, which might consist of the code for a particular telephone exchange. ITU-T recommendation E.123 describes how to represent an international telephone number in writing or print, starting with a plus sign and the country code. When calling an international number from a landline phone, the + must be replaced with the international call prefix chosen by the country the call is being made from.
Many mobile phones allow the + to be entered directly, by pressing and holding the "0" for GSM phones, or sometimes "*" for CDMA phones. The format and allocation of local phone numbers are controlled by each nation's respective government, either directly or by sponsored organizations. In the United States, each state's public service commission regulates, as does the Federal Communications Commission. In Canada, which shares the same country code with the U. S. regulation is through the Canadian Radio-television and Telecommunications Commission. Local number portability allows a subscriber to requ
1A2 Key Telephone System
The 1A2 Key Telephone System is a business telephone system developed and distributed by the Western Electric Company for the Bell System. The 1A2 Key Telephone System was a modular system that provided flexible solutions for a variety of telephone service requirements, it provided multiple users with control over multiple telephone lines without the requirement for an operator, system attendant, or receptionist. Each user could select a specific telephone line to place calls on, or to answer calls, manage those calls by placing them on hold or transferring them to other stations; the system provided options for station-to-station signaling and intercom, music-on-hold. The control functions were operated directly on each telephone instrument with a set of push buttons that had lamps installed internally to provide visual indication of line status. Introduced in 1964, the 1A2 system represents a stage of key telephone systems development at Bell Laboratories that started in the late 1930s with the 1A Key Telephone System, was an improvement over the 1A1 system introduced in 1953.
Compatible 1A2 equipment was manufactured by competing vendors, such as Northern Telecom, Automatic Electric, ITT, Stromberg-Carlson. The successor technologies to the 1A2 Systems include the AT&T Merlin, AT&T Spirit, AT&T Partner systems; the 1A2 Key Telephone System was produced to provide flexible solutions for varying telephone service requirements in businesses and enterprises. The 1A2 system used a modular plug-in construction concept that permitted many configurations using the same basic components. A typical system consisted of a basic metal mounting frame, the Key Service Unit called a panel, with card-edge connectors and mounting brackets for components and punch-down blocks for interconnecting cabling; the principal switching and control modules were constructed on printed circuit boards, called Key Telephone Units. KTUs provided many system features, such as various types of line interfaces, dial intercom, music-on-hold, alarms; each central office telephone line connected to the system required at least one KTU.
The mounting panels varied according to the complexity of the telephone system. Typical early 1A2 systems used the Type 584 panels; the 584C panel contained 13 KTUs. The 583 panel held 15 KTUs. For smaller installations, panels were available that housed all components, including the power supply and connecting blocks; these panels supported only four to six central office lines. The most used telephone sets for the 1A2 systems were modifications of the Bell System standard 500-series telephones for rotary dial systems, the 2500-series Touch-Tone desk sets. For key system operation these sets were equipped with a set of push-buttons and additional internal contact springs to control the additional operational features, resulting in a large variety of specialty telephones; such telephone sets were the types 565, 630, 631, 830, 831. Telephone sets could be equipped with Touch-Tone keypads. A power supply was either mounted within separately nearby; the power supply provided 24 VDC for relay operation, filtered 24 VDC for talk battery, 10 VAC for lamps, 18 VAC for buzzers, 90-110 VAC at 30Hz for ringers.
Lamp and signaling voltages were routed through a mechanical interrupter, to create lamp flash, lamp wink, interrupted buzzer and ringing. Wiring between system components and telephone sets was facilitated by Type 66 punch-down blocks. For each telephone line from the central office, a key system required five pairs of internal wires: The central office tip and ring leads, the station tip and ring wires, the A and A1 control leads, lamp power and lamp ground, the ring signaling pair; each connection to a telephone set required six wires from the key system: One pair carried the talk circuit, one pair carried control information, known as A-Leads, for that line, designated A and A1, the third pair carried current to a lamp for the specific line key position on the telephone set. A telephone set could operate as many lines. Most keysets with up to nine lines are connected to the system using a single 25-pair cable terminated with an Amphenol 50-position "MicroRibbon" connector. Sets with up to 19 line positions used a 50-pair cable and the large instruments with 29 line positions used 75 pairs on three connectors.
The Call Director model telephone had over 30 line key positions, used 100 pairs on four connectors. The keyset cables were routed to a wiring closet or wiring panel where the Key Service Unit was installed and were terminated on a 66 type punch block a model 66M1-50; each of these blocks could accept two 25-pair cables for termination. Cross-connect wire jumpers, consisting of three twisted pairs were installed between these blocks and the larger distribution connecting blocks within the KSU for each line provided to the telephone set. Large 1A2 installations had multiple wiring closets fed by branch cables extended from the central closet where the KSU was located. An example of this type of installation would be a multi-story building; the KSU and incoming lines might be in the basement, while each floor had a branch wiring closet to which the telephones on that floor were connected. A user could select any available telephone line by pressing the appropriate pickup key and taking the handset off-hook.
While on a telephone call, a user could place the call on hold by pressing the hold button
Telephony is the field of technology involving the development and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is intimately linked to the development of the telephone. Telephony is referred to as the construction or operation of telephones and telephonic systems and as a system of telecommunications in which telephonic equipment is employed in the transmission of speech or other sound between points, with or without the use of wires; the term is used to refer to computer hardware and computer network systems, that perform functions traditionally performed by telephone equipment. In this context the technology is referred to as Internet telephony, or voice over Internet Protocol; the first telephones were connected directly in pairs. Each user had a separate telephone wired to the locations he or she might wish to reach; this became inconvenient and unmanageable when people wanted to communicate with more than a few people.
The inventions of the telephone exchange provided the solution for establishing telephone connections with any other telephone in service in the local area. Each telephone was connected to the exchange via the local loop. Nearby exchanges in other service areas were connected with trunk lines and long distance service could be established by relaying the calls through multiple exchanges. Switchboards were manually operated by an attendant referred to as the "switchboard operator"; when a customer cranked a handle on the telephone, it turned on an indicator on the board in front of the operator, who would plug the operator headset into that jack and offer service. The caller had to ask for the called party by name by number, the operator connected one end of a circuit into the called party jack to alert them. If the called station answered, the operator disconnected their headset and completed the station-to-station circuit. Trunk calls were made with the assistance of other operators at other exchangers in the network.
In modern times, most telephones are plugged into telephone jacks. The jacks are connected by inside wiring to a drop wire. Cables bring a large number of drop wires from all over a district access network to one wire center or telephone exchange; when a telephone user wants to make a telephone call, equipment at the exchange examines the dialed telephone number and connects that telephone line to another in the same wire center, or to a trunk to a distant exchange. Most of the exchanges in the world are interconnected through a system of larger switching systems, forming the public switched telephone network. After the middle of the 20th century and data became important secondary users of the network created to carry voices, late in the century, parts of the network were upgraded with ISDN and DSL to improve handling of such traffic. Today, telephony uses digital technology in the provisioning of telephone systems. Telephone calls can be provided digitally, but may be restricted to cases in which the last mile is digital, or where the conversion between digital and analog signals takes place inside the telephone.
This advancement has reduced costs in communication, improved the quality of voice services. The first implementation of this, ISDN, permitted all data transport from end-to-end speedily over telephone lines; this service was made much less important due to the ability to provide digital services based on the IP protocol. Since the advent of personal computer technology in the 1980s, computer telephony integration has progressively provided more sophisticated telephony services and controlled by the computer, such as making and receiving voice and data calls with telephone directory services and caller identification; the integration of telephony software and computer systems is a major development in the evolution of office automation. The term is used in describing the computerized services of call centers, such as those that direct your phone call to the right department at a business you're calling. It's sometimes used for the ability to use your personal computer to initiate and manage phone calls.
CTI is not a new concept and has been used in the past in large telephone networks, but only dedicated call centers could justify the costs of the required equipment installation. Primary telephone service providers are offering information services such as automatic number identification, a telephone service architecture that separates CTI services from call switching and will make it easier to add new services. Dialed Number Identification Service on a scale is wide enough for its implementation to bring real value to business or residential telephone usage. A new generation of applications is being developed as a result of standardization and availability of low cost computer telephony links. Starting with the introduction of the transistor, invented in 1947 by Bell Laboratories, to amplification and switching circuits in the 1950s, through development of computer-based electronic switching systems, the public switched telephone network has evolved towards automation and digitization of signaling and audio transmissions.
Digital telephony is the use of digital electronics in the operation and provisioning of telephony systems and services. Since the 1960s a digital core network has replaced the traditional analog transmission and signaling systems, much of the access network has been digitized. Digital
A telephone line or telephone circuit is a single-user circuit on a telephone communication system. This is the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, also implies a single telephone number for billing purposes reserved for that user. Telephone lines are used to deliver landline telephone service and Digital subscriber line phone cable service to the premises. Telephone overhead lines are connected to the public switched telephone network. In 1878, the Bell Telephone Company began to use two-wire circuits from each user's telephone to end offices which performed any necessary electrical switching to allow voice signals to be transmitted to more distant telephones; these wires were copper, although aluminium has been used, were carried in balanced pairs of open wire, separated by about 25 cm on poles above the ground, as twisted pair cables. Modern lines may run underground, may carry analog or digital signals to the exchange, or may have a device that converts the analog signal to digital for transmission on a carrier system.
The customer end of that wire pair is connected to a data access arrangement. In most cases, two copper wires for each telephone line run from a home or other small building to a local telephone exchange. There is a central junction box for the building where the wires that go to telephone jacks throughout the building and wires that go to the exchange meet and can be connected in different configurations depending upon the subscribed telephone service; the wires between the junction box and the exchange are known as the local loop, the network of wires going to an exchange, the access network. The vast majority of houses in the U. S. are wired with 6-position modular jacks with four conductors wired to the house's junction box with copper wires. Those wires may be connected back to two telephone overhead lines at the local telephone exchange, thus making those jacks RJ14 jacks. More only two of the wires are connected to the exchange as one telephone line, the others are unconnected. In that case, the jacks in the house are RJ11.
Older houses have 4-conductor telephone station cable in the walls color coded with Bell System colors: red, yellow, black as 2-pairs of 22 AWG solid copper. Inside the walls of the house—between the house's outside junction box and the interior wall jacks—the most common telephone cable in new houses is Category 5 cable—4 pairs of 24 AWG solid copper. Inside large buildings, in the outdoor cables that run to the telephone company POP, many telephone lines are bundled together in a single cable using the 25-pair color code
A telephone exchange is a telecommunications system used in the public switched telephone network or in large enterprises. An exchange consists of electronic components and in older systems human operators that interconnect 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 used synonymously with central office, a Bell System term. A central office is defined as a building used to house the inside plant equipment of several telephone exchanges, each serving a certain geographical area; such an area has been referred to as the exchange. Central office locations may be identified in North America as wire centers, designating a facility from which a telephone obtains dial tone. For business and billing purposes, telephony carriers define rate centers, which in larger cities may be clusters of central offices, to define specified geographical locations for determining distance measurements.
In the United States and Canada, the Bell System established in the 1940s a uniform system of identifying central offices with a three-digit central office code, used as a prefix to subscriber telephone numbers. All central offices within a larger region aggregated by state, were assigned a common numbering plan area code. With the development of international and transoceanic telephone trunks driven by direct customer dialing, similar efforts of systematic organization of the telephone networks occurred in many countries in the mid-20th century. For corporate or enterprise use, a private telephone exchange is referred to as a private branch exchange, when it has connections to the public switched telephone network. A PBX is installed in enterprise facilities collocated with large office spaces or within an organizational campus to serve the local private telephone system and any private leased line circuits. Smaller installations might deploy a PBX or key telephone system in the office of a receptionist.
In the era of the electrical telegraph, post offices, railway stations, the more important governmental centers, stock exchanges few nationally distributed newspapers, the largest internationally important corporations and wealthy individuals were the principal users of such telegraphs. Despite the fact that telephone devices existed before the invention of the telephone exchange, their success and economical operation would have been impossible on the same schema and structure of the contemporary telegraph, as prior to the invention of the telephone exchange switchboard, early telephones were hardwired to and communicated with only a single other telephone. A telephone exchange is a telephone system located at service centers responsible for a small geographic area that provided the switching or interconnection of two or more individual subscriber lines for calls made between them, rather than requiring direct lines between subscriber stations; this made it possible for subscribers to call each other at businesses, or public spaces.
These made telephony an available and comfortable communication tool for everyday use, it gave the impetus for the creation of a whole new industrial sector. As with the invention of the telephone itself, the honor of "first telephone exchange" has several claimants. One of the first to propose a telephone exchange was Hungarian Tivadar Puskás in 1877 while he was working for Thomas Edison; the first experimental telephone exchange was based on the ideas of Puskás, it was built by the Bell Telephone Company in Boston in 1877. The world's first state-administered telephone exchange opened on November 12, 1877 in Friedrichsberg close to Berlin under the direction of Heinrich von Stephan. George W. Coy designed and built the first commercial US telephone exchange which opened in New Haven, Connecticut in January, 1878; the switchboard was built from "carriage bolts, handles from teapot lids and bustle wire" and could handle two simultaneous conversations. Charles Glidden is credited with establishing an exchange in Lowell, MA. with 50 subscribers in 1878.
In Europe other early telephone exchanges were based in London and Manchester, both of which opened under Bell patents in 1879. Belgium had its first International Bell exchange a year later. In 1887 Puskás introduced the multiplex switchboard.. Exchanges consisted of one to several hundred plug boards staffed by switchboard operators; each operator sat in front of a vertical panel containing banks of ¼-inch tip-ring-sleeve jacks, each of, the local termination of a subscriber's telephone line. In front of the jack panel lay a horizontal panel containing two rows of patch cords, each pair connected to a cord circuit; when a calling party lifted the receiver, the local loop current lit a signal lamp near the jack. The operator responded by inserting the rear cord into the subscriber's jack and switched her headset into the circuit to ask, "Number, please?" For a local call, the operator inserted the front cord of the pair into the called party's local jack and started the ringing cycle. For a long distance call, she plugged into a trunk circuit to connect to another operator in another bank of boards or at a remote central office.
In 1918, the average time to complete the connection for a long-distance call was 15 minutes. Early manual switchboards required the operator to operate listening keys and ringing keys, but by the late 1910s and 1920s, advances in switchboard technology led to features which allowed the call to be automatic
General Services Administration
The General Services Administration, an independent agency of the United States government, was established in 1949 to help manage and support the basic functioning of federal agencies. GSA supplies products and communications for U. S. government offices, provides transportation and office space to federal employees, develops government-wide cost-minimizing policies and other management tasks. GSA employs about 12,000 federal workers and has an annual operating budget of $20.9 billion. GSA oversees $66 billion of procurement annually, it contributes to the management of about $500 billion in U. S. federal property, divided chiefly among 8,700 owned and leased buildings and a 215,000 vehicle motor pool. Among the real estate assets managed by GSA are the Ronald Reagan Building and International Trade Center in Washington, D. C. – the largest U. S. federal building after the Pentagon – and the Hart-Dole-Inouye Federal Center. GSA's business lines include the Federal Acquisition Service and the Public Buildings Service, as well as several Staff Offices including the Office of Government-wide Policy, the Office of Small Business Utilization, the Office of Mission Assurance.
As part of FAS, GSA's Technology Transformation Services helps federal agencies improve delivery of information and services to the public. Key initiatives include FedRAMP, Cloud.gov, the USAGov platform, Data.gov, Performance.gov, Challenge.gov. GSA is a member of the Procurement G6, an informal group leading the use of framework agreements and e-procurement instruments in public procurement. In 1947 President Harry Truman asked former President Herbert Hoover to lead what became known as the Hoover Commission to make recommendations to reorganize the operations of the federal government. One of the recommendations of the commission was the establishment of an "Office of the General Services." This proposed office would combine the responsibilities of the following organizations: U. S. Treasury Department's Bureau of Federal Supply U. S. Treasury Department's Office of Contract Settlement National Archives Establishment All functions of the Federal Works Agency, including the Public Buildings Administration and the Public Roads Administration War Assets AdministrationGSA became an independent agency on July 1, 1949, after the passage of the Federal Property and Administrative Services Act.
General Jess Larson, Administrator of the War Assets Administration, was named GSA's first Administrator. The first job awaiting Administrator Larson and the newly formed GSA was a complete renovation of the White House; the structure had fallen into such a state of disrepair by 1949 that one inspector of the time said the historic structure was standing "purely from habit." Larson explained the nature of the total renovation in depth by saying, "In order to make the White House structurally sound, it was necessary to dismantle, I mean dismantle, everything from the White House except the four walls, which were constructed of stone. Everything, except the four walls without a roof, was stripped down, that's where the work started." GSA worked with President Truman and First Lady Bess Truman to ensure that the new agency's first major project would be a success. GSA completed the renovation in 1952. In 1986 GSA headquarters, U. S. General Services Administration Building, located at Eighteenth and F Streets, NW, was listed on the National Register of Historic Places, at the time serving as Interior Department offices.
In 1960 GSA created the Federal Telecommunications System, a government-wide intercity telephone system. In 1962 the Ad Hoc Committee on Federal Office Space created a new building program to address obsolete office buildings in Washington, D. C. resulting in the construction of many of the offices that now line Independence Avenue. In 1970 the Nixon administration created the Consumer Product Information Coordinating Center, now part of USAGov. In 1974 the Federal Buildings Fund was initiated, allowing GSA to issue rent bills to federal agencies. In 1972 GSA established the Automated Data and Telecommunications Service, which became the Office of Information Resources Management. In 1973 GSA created the Office of Federal Management Policy. GSA's Office of Acquisition Policy centralized procurement policy in 1978. GSA was responsible for emergency preparedness and stockpiling strategic materials to be used in wartime until these functions were transferred to the newly-created Federal Emergency Management Agency in 1979.
In 1984 GSA introduced the federal government to the use of charge cards, known as the GMA SmartPay system. The National Archives and Records Administration was spun off into an independent agency in 1985; the same year, GSA began to provide governmentwide policy oversight and guidance for federal real property management as a result of an Executive Order signed by President Ronald Reagan. In 2003 the Federal Protective Service was moved to the Department of Homeland Security. In 2005 GSA reorganized to merge the Federal Supply Service and Federal Technology Service business lines into the Federal Acquisition Service. On April 3, 2009, President Barack Obama nominated Martha N. Johnson to serve as GSA Administrator. After a nine-month delay, the United States Senate confirmed her nomination on February 4, 2010. On April 2, 2012, Johnson resigned in the wake of a management-deficiency report that detailed improper payments for a 2010 "Western Regions" training conference put on by the Public Buildings Service in Las Vegas.
In July 1991 GSA contractors began the excavation of what is now the Ted Weiss Federal Building in New York City. The planning for that buildin