Telephone call
A telephone call is a connection over a telephone network
Telephone network
A telephone network is a telecommunications network used for telephone calls between two or more parties.There are a number of different types of telephone network:...

 between the calling party
Calling party
The calling party is a person who initiates a telephone call over the public switched telephone network, usually by dialing a telephone number....

 and the called party
Called party
The called party is a person who answers a telephone call. The person who initiates a telephone call is the calling party....


Information transmission

A telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...

 call may carry ordinary voice
Human voice
The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about 60 to 7000 Hz. The human voice is specifically that part of human sound production in which the vocal folds are the primary...

 transmission using a telephone, data transmission
Data transmission
Data transmission, digital transmission, or digital communications is the physical transfer of data over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibres, wireless communication channels, and storage media...

 when the calling party and called party are using modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...

s, or facsimile
Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

 transmission when they are using fax
Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

 machines. The call may use land line, mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

, satellite phone
Satellite phone
A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites...

 or any combination thereof. Where a telephone call has more than one called party
Called party
The called party is a person who answers a telephone call. The person who initiates a telephone call is the calling party....

 it is referred to as a conference call
Conference call
A conference call is a telephone call in which the calling party wishes to have more than one called party listen in to the audio portion of the call. The conference calls may be designed to allow the called party to participate during the call, or the call may be set up so that the called party...

. When two or more users of the network are sharing the same physical line, it is called a party line
Party line (telephony)
In twentieth-century telephone systems, a party line is an arrangement in which two or more customers are connected directly to the same local loop. Prior to World War II in the United States, party lines were the primary way residential subscribers acquired local telephone service...

 or Rural phone line.

If the caller's wireline phone is directly connected to the calling party, when the caller takes their telephone off-hook
In telephony, 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. Note: off-hook originally referred to the condition that prevailed when telephones had a separate earpiece , which hung...

, the calling party's phone will ring. This is called a hot line or ringdown
-Operator signaling: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...

. Otherwise, the calling party is usually given a tone to indicate they should begin dialing the desired number. In some (now very rare) cases, the calling party cannot dial calls directly, and is connected to an operator
Telephone operator
A telephone operator is either* a person who provides assistance to a telephone caller, usually in the placing of operator assisted telephone calls such as calls from a pay phone, collect calls , calls which are billed to a credit card, station-to-station and person-to-person calls, and certain...

 who places the call for them.

Calls may be placed through a public network (such as the Public Switched Telephone Network
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...

) provided by a commercial telephone company
Telephone company
A telephone company is a service provider of telecommunications services such as telephony and data communications access. Many were at one time nationalized or state-regulated monopolies...

 or a private network called a PBX. In most cases a private network is connected to the public network in order to allow PBX users to dial the outside world. Incoming calls to a private network arrive at the PBX in two ways: either directly to a users phone using a DDI number
Direct Inward Dialing
Direct inward dialing , also called direct dial-in in Europe and Oceania, is a feature offered by telephone companies for use with their customers' private branch exchange systems...

 or indirectly via a receptionist who will answer the call first and then manually put the caller through to the desired user on the PBX.

Most telephone calls through the PSTN are set up using ISUP
ISDN User Part
The ISDN User Part or ISUP is part of the Signaling System #7 which is used to set up telephone calls in Public Switched Telephone Networks...

 signalling messages or one of its variants between telephone exchange
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...

s to establish the end to end connection. Calls through PBX networks are set up using QSIG
QSIG is an ISDN based signaling protocol for signaling between private branch exchanges in a Private Integrated Services Network . It makes use of the connection-level Q.931 protocol and the application-level ROSE protocol...

, DPNSS or variants.


Some types of calls are not charged, such as local call
Local call
In telephony, the term local call has the following meanings:# Any call using a single switching center; that is, not traveling to another telephone network;# A call made within a local calling area as defined by the local exchange carrier;...

s (and Internal calls) dialed directly by a telephone subscriber in Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...

, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 or New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 (Residential subscribers only). In most other areas, all telephone calls are charged a fee for the connection. Fees depend on the provider of the service, the type of service being used (a call placed from a landline
A landline was originally an overland telegraph wire, as opposed to an undersea cable. Currently, landline refers to a telephone line which travels through a solid medium, either metal wire or optical fibre, as distinguished from a mobile cellular line, where transmission is via radio waves...

 or wired telephone will have one rate, and a call placed from a mobile telephone will have a different rate) and the distance between the calling and the called parties. In most circumstances, the calling party pays this fee. However, in some circumstances such as a reverse charge
Reverse charge
Reverse charge may mean:* In placing telephone calls, reversing charges is also known as a Collect call.* With rechargeable batteries, a mistake in use or charging may lead to Reverse charging.* the accrual of VAT by the buyer of goods or services...

 or collect call
Collect call
A collect call in the USA and Canada or reverse charge call in the UK and other countries is a telephone call in which the calling party wants to place a call at the called party's expense...

, the called party pays the cost of the call. In some circumstances, the caller pays a flat rate
Flat rate
A flat fee, also referred to as a flat rate or a linear rate, refers to a pricing structure that charges a single fixed fee for a service, regardless of usage. Rarely, it may refer to a rate that does not vary with usage or time of use...

 charge for the telephone connection and does not pay any additional charge for all calls made. Telecommunication liberalization has been established in several countries to allows customers to keep their local phone provider and use an alternate provider for a certain call in order to save money.

Placing a call

A typical phone call using a traditional phone is placed by picking the phone handset up off the base and holding the handset so that the hearing end is next to the user's ear and the speaking end is within range of the mouth. The caller would then rotary dial
Rotary dial
The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send electrical pulses, known as pulse dialing, corresponding to the number dialed. The early form of the rotary dial used lugs on a finger plate instead of holes. Almon Brown Strowger filed the first patent...

 or press buttons for the phone numbers needed to complete the call.

In addition to the traditional method of placing a telephone call, new technologies allow different methods for initiating a telephone call, such as voice dialing. Voice over IP
Voice over IP
Voice over Internet Protocol is a family of technologies, methodologies, communication protocols, and transmission techniques for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet...

 technology allows calls to be made through a PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

, using a service like Skype
Skype is a software application that allows users to make voice and video calls and chat over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system...

. Other services enable callers to initiate a telephone call through a third party without exchanging phone numbers.

The use of headsets
Headset (telephone/computer)
A headset is headphones combined with a microphone, or one headphone with a microphone. Headsets provide the equivalent functionality of a telephone handset with hands-free operation. Headsets typically have only one speaker like a telephone, but also come with speakers for both ears...

 is becoming more common for placing or receiving a call. Headsets can either come with a cord or be wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...



Preceding, during, and after a traditional telephone call is placed, certain tones signify the progress and status of the telephone call:
  • a dial tone
    Dial tone
    A dial tone is a telephony signal used to indicate that the telephone exchange is working, has recognized an off-hook, and is ready to accept a call. The tone stops when the first numeral is dialed...

     signifying that the system is ready to accept a telephone number
    Telephone number
    A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given orally to a switchboard operator...

     and connect the call
  • either:
    • a ringing tone
      Ringback tone
      A ringback tone is an audible indication that is heard on the telephone line by the caller while the phone they are calling is being rung. It is normally a repeated tone, designed to assure the calling party that the called party's line is ringing, although the ring-back tone may be out of sync...

       signifying that the calling party has yet to answer the telephone
    • a busy signal (or engaged tone) signifying that the calling party's telephone is being used in a telephone call to another person (or is "off the hook" though no number has been dialled, i.e. the customer does not want to be disturbed)
    • a fast busy signal (also called reorder tone
      Reorder tone
      The reorder tone, also known as the fast busy tone, is the congestion tone or all trunks busy tone of a public switched telephone network. It varies from country to country; in the USA it is a dual-frequency tone of 480 Hz and 620 Hz at a cadence of 0.25 seconds on, 0.25 off; that is two beeps per...

       or overflow busy tone) signifying that there is congestion in the telephone network, or possibly that the calling subscriber has delayed too long in dialling all the necessary digits. The fast busy signal is generally twice as fast as the normal busy signal.
  • status tones
    Status tones
    Status Tones are short tones that are generated and placed on the Telephone Line while a call is being initiated, while it is being conducted, and while it is being monitored by a third party to inform all on the line of an actve or defined event....

     such as STD notification tones (to inform the caller that the telephone call is being trunk dialled
    Subscriber trunk dialling
    Subscriber trunk dialling is a term for a telephone system allowing subscribers to dial trunk calls without operator assistance.- Terminology :...

     at a greater cost to the calling party), minute minder beeps (to inform the caller of the relative duration of the telephone call on calls that are charged on a time basis), and others
  • a tone (sometimes the busy signal, often the dial tone) to signify that the called party has hung up.
  • tones used by earlier inband
    In-band signaling
    In telecommunications, in-band signaling is the sending of metadata and control information in the same band or channel used for data.-Telephone:...

     telephone switching systems were simulated by a Red box or a blue box used by "phone phreaks
    Phreaking is a slang term coined to describe the activity of a culture of people who study, experiment with, or explore telecommunication systems, such as equipment and systems connected to public telephone networks. As telephone networks have become computerized, phreaking has become closely...

    " to illegally make or receive free trunk/toll calls.

Unwanted calls

Unsolicited telephone calls are a modern nuisance. Common kinds of unwanted calls include prank call
Prank call
A prank call is a form of practical joke committed over the telephone. Prank phone calls began to gain an America-wide following over a period of many years, as they gradually became a staple of the obscure and amusing cassette tapes traded amongst musicians, sound engineers, and media traders...

s, telemarketing
Telemarketing is a method of direct marketing in which a salesperson solicits prospective customers to buy products or services, either over the phone or through a subsequent face to face or Web conferencing appointment scheduled during the call.Telemarketing can also include recorded sales pitches...

 calls, and obscene phone call
Obscene phone call
An obscene phone call is an unsolicited telephone call where a person derives sexual pleasure by using sexual or foul language to an unknown person. Making obscene telephone calls for sexual pleasure is known as telephone scatologia and is considered a form of exhibitionism...


Caller ID
Caller ID
Caller ID , also called calling line identification or calling number identification or Calling Line Identification Presentation , is a telephone service, available in analog and digital phone systems and most Voice over Internet Protocol applications, that transmits a caller's number to...

 provides some protection against unwanted calls, but can still be turned off by the calling party. Even where end-user Caller ID is not available, calls are still logged, both in billing records at the originating telco and via automatic number identification
Automatic number identification
Automatic number identification is a feature of telephony intelligent network services that permits subscribers to display or capture the billing telephone number of a calling party. In the United States it is part of Inward Wide Area Telephone Service . ANI service was created by AT&T for...

, so the perpetrator's phone number can still be discovered in many cases. However, this does not provide complete protection: harassers can use payphones, in some cases, automatic number identification itself can be spoofed or blocked, and mobile telephone abusers can (at some cost) use "throwaway" phones or SIMs.


  • Rabinow, J., -- "Telephone call indicator" -- November 12, 1957

See also

  • Teletraffic engineering
    Teletraffic engineering
    Telecommunications traffic engineering, teletraffic engineering, or traffic engineering is the application of traffic engineering theory to telecommunications...

  • Call processing
    Call processing
    In telecommunication, the term call processing has the following meanings:# The sequence of operations performed by a switching system from the acceptance of an incoming call through the final disposition of the call...

  • Call completion
    Call completion
    Call Completion is a telephony feature allowing some form of alternative interaction between parties who cannot converse directly with each other.There are several possible factors which can prevent a telephone call from connecting successfully:...

  • Pocket dialing
    Pocket Dialing
    Pocket dialing refers to the accidental placement of a phone call while a person's mobile phone in the dialer's pocket or handbag. The recipient of the call typically hears random background noise when they answer the phone...

  • Telephone phobia
    Telephone phobia
    Telephone phobia is reluctance or fear of making or taking phone calls, literally, "fear of telephone"...

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