A softphone is a

software Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work. ...

program for making

telephone 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 e ...

calls over the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

using a general purpose computer rather than dedicated hardware. The softphone can be installed on a piece of equipment such as a

desktop A desktop traditionally refers to: * The surface of a desk (often to distinguish office appliances that fit on a desk, such as photocopiers and printers, from larger equipment covering its own area on the floor) Desktop may refer to various compu ...

mobile device A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physica ...

, or other computer and allows the user to place and receive calls without requiring an actual telephone set. Often, a softphone is designed to behave like a traditional telephone, sometimes appearing as an image of a

handset A handset is a component of a telephone that a user holds to the ear and mouth to receive audio through the receiver and speak to the remote party using the built-in transmitter. In earlier telephones, the transmitter was mounted directly on ...

, with a display panel and buttons with which the user can interact. A softphone is usually used with a headset connected to the

sound card A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio ...

of the PC or with a

USB phone A USB phone looks like a traditional telephone, but it has a USB connector instead of an RJ-11. It may be used with most softphones and services like Skype, Sipnet, Sippoint Mini, Net2Phone, MSN Messenger, NetMeeting, Xlite, Skype for Business ...

Applications

See Comparison of VoIP software

Communication protocols

To communicate, both end-points must support the same voice-over-IP protocol, and at least one common audio

codec A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or ...

. Many service providers use the Session Initiation Protocol (SIP) standardized by the

Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

(IETF).

Skype Skype () is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls. It also has instant messaging, file transfer, deb ...

, a popular service, uses proprietary protocols, and Google Talk leveraged the Extensible Messaging and Presence Protocol (XMPP). Some softphones also support the

Inter-Asterisk eXchange Inter-Asterisk eXchange (IAX) is a communications protocol native to the Asterisk private branch exchange (PBX) software, and is supported by a few other softswitches, PBX systems, and softphones. It is used for transporting VoIP telephony session ...

protocol (IAX), a protocol supported by the open-source software application ''Asterisk''.

Features

A typical softphone has all standard telephony features (DND, Mute,

DTMF Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. DTMF was first developed ...

, Flash, Hold, Transfer etc.) and often additional features typical for online messaging, such as user presence indication, video, wide-band audio. Softphones provide a variety of audio codecs, a typical minimum set is G.711 and G.729.

Requirements

To make voice calls via the Internet, a user typically requires the following: * A modern PC with a microphone and speaker, or with a headset, or USB phone. * Reliable high-speed Internet connectivity like digital subscriber line (DSL), or cable service. * Account with an Internet telephony service provider or

IP PBX An IP PBX ("Internet Protocol private branch exchange") is a system that connects telephone extensions to the public switched telephone network (PSTN) and provides internal communication for a business. An IP PBX is a PBX system with IP connectivi ...

provider. * Mobile or landline phone.

References

{{Telecommunications VoIP software

Applications

Communication protocols

Features

Requirements

See also

References