VoIP phone

IP PhoneIP PhonesEthernet-based phoneIPIP desktop phoneIP telephoneIP telephonesphoneVoIPVoIP phone service
A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet, instead of the traditional public switched telephone network (PSTN).wikipedia
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Voice over IP

VoIPvoice over Internet Protocolvoice-over-IP
A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet, instead of the traditional public switched telephone network (PSTN). VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone. Various schemes exist to allow one Internet telephony user to talk to another entirely via Internet and without incurring the cost of a PSTN call. Some are based on SIP addresses, some on proprietary protocol such as webcam or Internet chat applications. While it's not uncommon for two clients of the same voice over IP provider to talk to each other online for free, the various Internet telephony applications often do not talk directly to each other - requiring calls be gated to PSTN and back at full toll rates.
In addition to VoIP phones, VoIP is also available on many personal computers and other Internet access devices.

Session Initiation Protocol

SIPSession Initiation Protocol (SIP)SIP Trunking
Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol (SIP), Skinny Client Control Protocol (SCCP) or various other proprietary protocols.
A SIP phone is an IP phone that implements client and server functions of a SIP user agent and provides the traditional call functions of a telephone, such as dial, answer, reject, call hold, and call transfer.

Telephone

phonetelephonesLocal Telephone Service
VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone.
The customer equipment may be an analog telephone adapter (ATA) which interfaces a conventional analog telephone to the IP networking equipment, or it may be an IP Phone that has the networking and interface technology built into the desk-top set and provides the traditional, familiar parts of a telephone, the handset, the dial or keypad, and a ringer in a package that usually resembles a standard telephone set.

Power over Ethernet

PoE802.3at802.3af
Power source - a battery or DC/AC source; some VoIP phones receive electricity from Power over Ethernet
This allows a single cable to provide both data connection and electric power to devices such as wireless access points, IP cameras, and VoIP phones.

Softphone

soft phonePC-to-PC calling
VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone.
VoIP phone

Voice engine

A voice engine or a digital signal processor (DSP) to process RTP messages. Some IC manufacturers provides GPP and DSP in single chip
Voice engines handle the voice processing for an IP Phone system on a standard processor, compared to prior generations of systems which required dedicated, math-optimized digital signal processor chips.

Caller ID spoofing

spoofspoofeda false origin is displayed
Caller ID display
If the caller name is sent with the call (instead of being generated from the number by a database lookup at destination) it may be configured as part of the settings on a client-owned analog telephone adapter or SIP phone.

SIP URI scheme

Various schemes exist to allow one Internet telephony user to talk to another entirely via Internet and without incurring the cost of a PSTN call. Some are based on SIP addresses, some on proprietary protocol such as webcam or Internet chat applications. While it's not uncommon for two clients of the same voice over IP provider to talk to each other online for free, the various Internet telephony applications often do not talk directly to each other - requiring calls be gated to PSTN and back at full toll rates.
As the client may be a SIP phone or other device with just a numeric, telephone-like keypad, various schemes exist to associate an entirely numeric identifier to a publicly reachable SIP address.

Mobile phone

cell phonemobilemobile phones
There are several Wi-Fi enabled mobile phones and PDAs that have pre-installed SIP client software, or are capable of running IP telephony clients, including most smartphones.
VoIP phone

Extension Mobility

Accounts are usually set and memorized on the phone itself. A more sophisticated feature is dynamic download of account settings, also known as "extension mobility". This feature allows settings stored on a server to be downloaded to the phone, based on user login. The user logs into the phone and that phone becomes the user's extension. This feature requires both a client (phone) and a server, usually in the context of unif ied communications systems.
The Cisco Extension Mobility feature, sometimes referred to as hoteling, allows a user to temporarily configure another IP telephone as his own.

Telephone call

callphone callphone calls
A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet, instead of the traditional public switched telephone network (PSTN).

Internet

onlinethe Internetweb
A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet, instead of the traditional public switched telephone network (PSTN).

Proprietary protocol

proprietaryproprietary networking protocolproprietary communications protocol
Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol (SIP), Skinny Client Control Protocol (SCCP) or various other proprietary protocols.

Cordless telephone

cordless phonecordless phonescordless
VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone.

Analog telephone adapter

analog telephony adapterATAAnalogue Telephone Adaptors
Traditional PSTN phones are used as VoIP phones with analog telephone adapters (ATA).

Skype

SkypingSkype PreviewMicrosoft Skype
Generally the features of VoIP phones follow those of Skype and other PC-based phone services, which have richer feature sets but (because they rely on mainstream operating systems' IP support) latency-related audio problems.

Quality of service

QoSquality-of-serviceQuality of Service (QOS)
A competing view is that as mainstream operating systems become better at voice applications with appropriate Quality of Service (QoS) guarantees and 5G handoff (IEEE 802.21 etc.) becomes available from outdoor wireless carriers, netbooks and smartphones will simply become the dominant interfaces.

5G

5G NR5th generation mobile networks3GPP 5G New Radio (NR) standards,
A competing view is that as mainstream operating systems become better at voice applications with appropriate Quality of Service (QoS) guarantees and 5G handoff (IEEE 802.21 etc.) becomes available from outdoor wireless carriers, netbooks and smartphones will simply become the dominant interfaces.

IEEE 802.21

802.21
A competing view is that as mainstream operating systems become better at voice applications with appropriate Quality of Service (QoS) guarantees and 5G handoff (IEEE 802.21 etc.) becomes available from outdoor wireless carriers, netbooks and smartphones will simply become the dominant interfaces.

Netbook

netbooksmini laptop
A competing view is that as mainstream operating systems become better at voice applications with appropriate Quality of Service (QoS) guarantees and 5G handoff (IEEE 802.21 etc.) becomes available from outdoor wireless carriers, netbooks and smartphones will simply become the dominant interfaces.

Smartphone

smartphonessmart phonesmart phones
There are several Wi-Fi enabled mobile phones and PDAs that have pre-installed SIP client software, or are capable of running IP telephony clients, including most smartphones. A competing view is that as mainstream operating systems become better at voice applications with appropriate Quality of Service (QoS) guarantees and 5G handoff (IEEE 802.21 etc.) becomes available from outdoor wireless carriers, netbooks and smartphones will simply become the dominant interfaces.

IPhone

iPhonesiPhone appApple iPhone
iPhone, Android and the QNX OS used in 2012-and-later BlackBerry phones are generally capable of VoIP performance even on small battery-charged devices.

Android (operating system)

AndroidAndroid operating systemAndroid OS
iPhone, Android and the QNX OS used in 2012-and-later BlackBerry phones are generally capable of VoIP performance even on small battery-charged devices.

QNX

NeutrinoQNX NeutrinoQNX Momentics IDE
iPhone, Android and the QNX OS used in 2012-and-later BlackBerry phones are generally capable of VoIP performance even on small battery-charged devices.