Telephony

digital telephonytelephonedigitaltelephone systemtelephonicvoicedigital telephonephonetelephone servicedigital telephone communication system
Telephony is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties.wikipedia
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Local loop

subscriber lineloopsubscriber loop
Each telephone was connected to the exchange via one wire pair, the local loop.
In telephony, the local loop (also referred to as a local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the common carrier or telecommunications service provider's network.

Pulse-code modulation

PCMlinear PCMLPCM
End-to-end analog telephone networks were first modified in the early 1960s by upgrading transmission networks with Digital Signal 1 (DS1/T1) carrier systems, designed to support the basic 3 kHz voice channel by sampling the bandwidth-limited analog voice signal and encoding using PCM.
It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications.

Telephone

phonetelephonesLocal Telephone Service
The history of telephony is intimately linked to the invention and development of the telephone.
With the development of electronic switching systems in the 1960s, telephony gradually evolved towards digital telephony which improved the capacity, quality, and cost of the network.

Digital subscriber line

DSLxDSLDigital Subscriber Line (DSL)
After the middle of the 20th century, fax and data became important secondary users of the network created to carry voices, and late in the century, parts of the network were upgraded with ISDN and DSL to improve handling of such traffic.
A naked DSL (also known as standalone or dry loop DSL) is a way of providing DSL services without a PSTN (analogue telephony) service.

Signalling System No. 7

SS7SS7 NetworkCCS7
development of SS7
Signaling System No. 7 (SS7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down most of the world's public switched telephone network (PSTN) telephone calls.

Companding

compandercompandedcompandor
non-linear quantization: A-law vs. μ-law, and transcoding between the two
Companding is employed in telephony and other audio applications such as professional wireless microphones and analog recording.

Public switched telephone network

PSTNtelephone networkpublic telephone network
Most of the exchanges in the world are interconnected through a system of larger switching systems, forming the public switched telephone network (PSTN).
The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication.

Multiplexing

multiplexedmultiplexmultiplexes
Although analog carrier systems existed that multiplexed multiple analog voice channels onto a single transmission medium, digital transmission allowed lower cost and more channels multiplexed on the transmission medium.
In telephony, a customer's telephone line now typically ends at the remote concentrator box, where it is multiplexed along with other telephone lines for that neighborhood or other similar area.

Voice over IP

VoIPvoice over Internet Protocolvoice-over-IP
In this context the technology is specifically referred to as Internet telephony, or voice over Internet Protocol (VoIP).
The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony and involve signaling, channel setup, digitization of the analog voice signals, and encoding.

Speech coding

speech codecspeech encodingspeech
digital speech coding and compression
From this point of view, the A-law and μ-law algorithms (G.711) used in traditional PCM digital telephony can be seen as an earlier precursor of speech encoding, requiring only 8 bits per sample but giving effectively 12 bits of resolution.

Mobile phone

cell phonemobilemobile phones
In addition to replacing plain old telephone service (POTS), IP telephony services compete with mobile phone services by offering free or lower cost connections via WiFi hotspots.
In addition to telephony, 2000s-era mobile phones support a variety of other services, such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, video games, and digital photography.

Videotelephony

videoconferencingvideo conferencingvideo chat
Video telephony restores such interactions to varying degrees.
This was first embodied in the device which came to be known as the video telephone, or videophone, and it evolved from intensive research and experimentation in several telecommunication fields, notably electrical telegraphy, telephony, radio, and television.

Disruptive innovation

disruptive technologydisruptive technologiesdisruption
VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone infrastructure technologies.

Computer network

networknetworkingcomputer networking
A specialization of digital telephony, Internet Protocol (IP) telephony involves the application of digital networking technology that was the foundation to the Internet to create, transmit, and receive telecommunications sessions over computer networks.
Examples of end-to-end encryption include HTTPS for web traffic, PGP for email, OTR for instant messaging, ZRTP for telephony, and TETRA for radio.

Telecommunication

telecommunicationscommunicationstelecom
Telephony is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties.

Telephone exchange

exchangescentral officeexchange
The inventions of the telephone exchange provided the solution for establishing telephone connections with any other telephone in service in the local area.

Trunking

trunktrunk linetrunks
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.

Switchboard operator

telephone operatoroperatoroperators
Initially, switchboards were manually operated by an attendant, commonly referred to as the "switchboard operator".

Telephone plug

telephone jackphone jackjack
In modern times, most telephones are plugged into telephone jacks.

On-premises wiring

customer premisescustomer premises wiringinside wiring
The jacks are connected by inside wiring to a drop wire which connects the building to a cable.

Drop (telecommunication)

dropdownlead
The jacks are connected by inside wiring to a drop wire which connects the building to a cable.

Access network

accessaccess attemptaccess networks
Cables usually bring a large number of drop wires from all over a district access network to one wire center or telephone exchange.

Telephone call

callphone callphone calls
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.

Telephone number

phone numbertelephone numbersphone numbers
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.

Telephone line

phone linelinetelephone lines
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.