Telephone line

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Utility pole with electric lines (top) and telephone cables. Phone pole3.jpg
Utility pole with electric lines (top) and telephone cables.
Fixed telephone lines per 100 inhabitants, 1997-2007. Fixed telephone lines per 100 inhabitants 1997-2007 ITU.png
Fixed telephone lines per 100 inhabitants, 1997–2007.
Cross section of telephone cable of 1,800 twisted pairs, 1922. Bell telephone magazine (1922) (14754023254).jpg
Cross section of telephone cable of 1,800 twisted pairs, 1922.

A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. [1] It is the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually 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 (DSL) phone cable service to the premises. Telephone overhead lines are connected to the public switched telephone network. The voltage at a subscriber's network interface is typically 48 V between the ring and tip wires, with tip near ground and ring at –48 V.

Contents

In the United States

In 1878, the Bell Telephone Company began to use two-wire circuits, called the local loop, 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 typically copper, although aluminium has also been used, and were carried in balanced pairs of open wire, separated by about 25 cm (10″) on poles above the ground, and later as twisted pair cables. Modern lines may run underground, and 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.

Often the customer end of that wire pair is connected to a data access arrangement; the telephone company end of that wire pair is connected to a telephone hybrid.

In most cases, two copper wires (tip and ring) 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, and the network of wires going to an exchange is known as the access network.

The vast majority of houses in the U.S. are wired with 6-position modular jacks with four conductors (6P4C) wired to the house's junction box with copper wires. Those copper wires may be connected back to two telephone overhead lines at the local telephone exchange, thus making those jacks RJ14 jacks. More often, only two of the wires are connected to the exchange as one telephone line, and the others are unconnected. In that case, the jacks in the house are RJ11.

Older houses often have 4-conductor telephone station cable in the walls color coded with Bell System colors: red, green, yellow, black as 2-pairs of 22 AWG (0.33 mm2) solid copper; "line 1" uses the red/green pair and "line 2" uses the yellow/black pair. 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 (0.205 mm2) solid copper. [2]

Inside large buildings, and 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. [3]

Outside plant cables can have up to 3,600 or 3,800 pairs, used at the entrances|| of telephone exchanges. [4] [5]

Related Research Articles

<span class="mw-page-title-main">Telephone</span> Telecommunications device

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 Greek: τῆλε and φωνή, together meaning distant voice. A common short form of the term is phone, which came into use early in the telephone's history. Nowadays, phones are almost always in the form of smartphones or mobile phones, due to technological convergence.

Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit.

Digital subscriber line is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for Internet access.

<span class="mw-page-title-main">Main distribution frame</span>

In telephony, a main distribution frame is a signal distribution frame for connecting equipment to cables and subscriber carrier equipment.

<span class="mw-page-title-main">Network topology</span> Arrangement of a communication network

Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.

<span class="mw-page-title-main">Category 5 cable</span> Unshielded twisted pair communications cable

Category 5 cable (Cat 5) is a twisted pair cable for computer networks. Since 2001, the variant commonly in use is the Category 5e specification (Cat 5e). The cable standard provides performance of up to 100 MHz and is suitable for most varieties of Ethernet over twisted pair up to 2.5GBASE-T but more commonly runs at 1000BASE-T speeds. Cat 5 is also used to carry other signals such as telephone and video.

<span class="mw-page-title-main">Remote concentrator</span>

In modern telephony a remote concentrator, remote concentrator unit (RCU), or remote line concentrator (RLC) is a concentrator at the lowest level in the telephone switch hierarchy.

<span class="mw-page-title-main">Twisted pair</span> Type of wiring used for communications

Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced pair, a twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighbouring pairs and improves rejection of external electromagnetic interference. It was invented by Alexander Graham Bell.

Plain Old Telephone Service (POTS), or Plain Ordinary Telephone System, is a retronym for voice-grade telephone service employing analog signal transmission over copper loops. Originally POTS stood for Post Office Telephone Service as early phone lines in most parts of the world were operated directly by the local Post Office.

<span class="mw-page-title-main">DSLAM</span> Network device that connects DSL interfaces to a digital communications channel

A digital subscriber line access multiplexer is a network device, often located in telephone exchanges, that connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital communications channel using multiplexing techniques. Its cable internet (DOCSIS) counterpart is the cable modem termination system.

<span class="mw-page-title-main">Demarcation point</span> Boundary of a private and public network

In telephony, the demarcation point is the point at which the public switched telephone network ends and connects with the customer's on-premises wiring. It is the dividing line which determines who is responsible for installation and maintenance of wiring and equipment—customer/subscriber, or telephone company/provider. The demarcation point varies between countries and has changed over time.

<span class="mw-page-title-main">Registered jack</span> Telecommunication network interface

A registered jack (RJ) is a standardized telecommunication network interface for connecting voice and data equipment to a computer service provided by a local exchange carrier or long distance carrier. Registered interfaces were first defined in the Universal Service Ordering Code (USOC) system of the Bell System in the United States for complying with the registration program for customer-supplied telephone equipment mandated by the Federal Communications Commission (FCC) in the 1970s. They were subsequently codified in title 47 of the Code of Federal Regulations Part 68. Registered jack connections began to see use after their invention in 1973 by Bell Labs. The specification includes physical construction, wiring, and signal semantics. Accordingly, registered jacks are primarily named by the letters RJ, followed by two digits that express the type. Additional letter suffixes indicate minor variations. For example, RJ11, RJ14, and RJ25 are the most commonly used interfaces for telephone connections for one-, two-, and three-line service, respectively. Although these standards are legal definitions in the United States, some interfaces are used worldwide.

The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists of telephone lines, fiber-optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables interconnected by switching centers, such as central offices, network tandems, and international gateways, which allow telephone users to communicate with each other.

<span class="mw-page-title-main">66 block</span> Table used to physically connect phone lines

A 66 block is a type of punch-down block used to connect sets of wires in a telephone system. They have been manufactured in four common configurations, A, B, E and M. A and B styles have the clip rows on 0.25" centers while E and M have the clip rows on 0.20" centers. The A blocks have 25 slotted holes on the left side for position the incoming building cable with a 50 slot fanning strip on the right side for distribution cables. They have been obsolete for many years. The B & M styles have 50 slot fanning strip on both sides. The B style is used mainly in distribution panels where several destinations need to connect to the same source. The M blocks are often used to connect a single instrument to such a distribution block. The E style has 5 columns of 10 2 clips rows and are used for transitioning from the 25 pair distribution cable to a 25 pair RJ21 style female ribbon connector.

A party line is a local loop telephone circuit that is shared by multiple telephone service subscribers.

<span class="mw-page-title-main">Tip and ring</span> Conductors of a telephone line

Tip and ring are the two conductors or sides of a telephone line. Their names are derived from the telephone plugs used for connecting telephone calls in manual switchboards. One side of the line is connected to the metal tip of the plug, and the second is connected to a metal ring behind the tip, separated and insulated from the tip by a non-conducting material. When inserted into a jack, the plug's tip conductor connects first, followed by the ring conductor. In many European countries, tip and ring are referred to as the A and B wires.

<span class="mw-page-title-main">British telephone socket</span> Type of telephone socket design

British telephone sockets were introduced in their current plug and socket form on 19 November 1981 by British Telecom to allow subscribers to connect their own telephones. The connectors are specified in British Standard BS 6312. Electrical characteristics of the telephone interface are specified by individual network operators, e.g. in British Telecom's SIN 351. Electrical characteristics required of British telephones used to be specified in BS 6305.

<span class="mw-page-title-main">ADSL</span> DSL service where downstream bandwidth exceeds upstream bandwidth

Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. ADSL differs from the less common symmetric digital subscriber line (SDSL). In ADSL, bandwidth and bit rate are said to be asymmetric, meaning greater toward the customer premises (downstream) than the reverse (upstream). Providers usually market ADSL as an Internet access service primarily for downloading content from the Internet, but not for serving content accessed by others.

Ringing is a telecommunication signal that causes a bell or other device to alert a telephone subscriber to an incoming telephone call. Historically, this entailed sending a high-voltage alternating current over the telephone line to a customer station which contained an electromagnetic bell. It is therefore also commonly referred to as power ringing, to distinguish it from another signal, audible ringing, or ringing tone, which is sent to the originating caller to indicate that the destination telephone is in fact ringing.

<span class="mw-page-title-main">Telephone exchange</span> Interconnects telephones for calls

A telephone exchange, also known as a telephone switch or central office, is a crucial component in the public switched telephone network (PSTN) or large enterprise telecommunications systems. It facilitates the interconnection of telephone subscriber lines or digital system virtual circuits, enabling telephone calls between subscribers.

References

  1. ↑ "Telephone Circuits". ScienceDirect . Retrieved 2022-12-12.
  2. ↑ Public Service Commission of Wisconsin. "Testing, Repairing & Installing Home Telephone Wiring" Archived 2018-03-28 at the Wayback Machine .
  3. ↑ Bigelow, Stephen J. (1993). Telephone repair illustrated (1st ed.). Blue Ridge Summit, PA: TAB Books. ISBN   0-8306-4034-7. OCLC   26632919.
  4. ↑ Wilkens, W.D. (March 1990). "Telephone cable: overview and dielectric challenges". IEEE Electrical Insulation Magazine. 6 (2): 23–28. doi:10.1109/57.50802. ISSN   0883-7554. S2CID   39098621.
  5. ↑ https://www.google.com.pa/books/edition/Doing_Business_with_Saudi_Arabia/or08gGGX_toC?hl=en&gbpv=1&dq=3800+pair+telephone+cable&pg=PA469&printsec=frontcover


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