Sofia-SIP is an open-source SIP User-Agent library, compliant with the IETF RFC3261 specification. It can be used as a building block for SIP client software for uses such as VoIP, IM, and many other real-time and person-to-person communication services.
Solid PBX is a multi-platform Soft Switch Class 5 software targeted for home/corporate/operator level markets.
Speak Freely is an application for a variety of Unix workstations that allows you to talk (actually send voice, not typed characters) over a network.
TalKT is a very simple application which allows voice QSO over packet. It uses a very simple but flexible protocol called VoAX to transfer data.
Tapioca is a framework for Voice over IP (VoIP) and IM applications. Its main goal is to provide an easy way to develop and use VoIP/IM services in any kind of application. It provides a pluggable interface for different protocols, such as SIP/XMPP.
TkPhone is an application that allows to record telephone numbers in books, select the book you want to browse, select the name of that book you want to call and, if you are connected to a modem and you have the right permissions, call that number.
TkVoice is a Telephone Answering Machine (TAM) front-end for vgetty. It provides a GUI under X-11, KDE, or GNOME and allows the user to record an outgoing greeting. They can then play back incoming voice messages.
ToothMote is an application to control Linux computers using a BlueTooth enabled cell phone. This program provides a basis for communicating with a connected cell phone, and then uses a plugin architecture to easily expand the amount of functionality it provides.
Tox provides an easy to use application that allows you to connect with friends and family without anyone else listening in. While other big-name services require you to pay for features, Tox is totally free, and comes without advertising.
tsemgr is a GTK+ application to manage the SonyEricsson T68 mobile phone. You can read and send short messages (SMS), view and edit the phonebook, upload files and turn your phone into a remote control for your linux box.
TuxCall detects voice calls and hangs up the connection, allowing
you to answer the phone.
Twinkle is a soft phone for your voice over IP communcations using the SIP protocol. You can use it for direct IP phone to IP phone communication or in a network using a SIP proxy to route your calls. Read more
USB Headset Buttons
USB Headset Buttons is a tool that enables the volume control buttons on a Logitech USB 30 Headset or similar device.
vat is a real-time, multi-party, multimedia application for audio conferencing over the Internet.
VOCAL provides the development community with software and tools needed to build new and exciting VoIP features, applications and services. The software in VOCAL includes a SIP based Redirect Server, Feature Server, Provisioning Server, Policy Server and Marshal Proxy along with protocol translators from SIP to H.323 and SIP to MGCP.
VoiceChat allows transferring bidirectional audio data in almost real time over a TCP/IP network such as the Internet. It is meant for two-person voice conversations, much like the telephone.
The vomit utility converts a Cisco IP phone conversation into a wave file that can be played with ordinary sound players. Vomit requires a tcpdump output file. Vomit is not a VoIP sniffer also it could be but the naming is probably related to H.323.
Walkietalkie is a program which allows full duplex voice communications over the internet. All you need is a PC or Mac and a microphone. It is free to use and distribute. It just streams audio between two points on the internet, there are no servers, so it can't be regulated or taken away.
Whisper is an easy to use internet phone. Whisper uses gsm compression and is usable over low bandwidth networks (19.200 bps and up).
WombatDialer is highly scalable, multi-server, easy-to-use telecasting platform for your Asterisk PBX. This can be used to implement many different services. By offering you a set of ready-to-use components and a monitoring GUI, you can create complex solution in minutes.
wxDialer is a simple and easy to use dialer program, roughly based on the win9x program 'dialer.exe' - all it does is allow you to make and recieve calls on your modem. A microphone is required, and it is suggested that you also have headphones instead of using your speakers to prevent any nasty feedback. A telephone headset, naturally, is best for this.
X PHONE allows you to use your modem as a half duplex speaker phone, if your modem has a speaker jack and if you have amplified speakers. Just plug your speakers in and run X PHONE for instant phone fidelity.
x70talk is an application to allow communication with a Panasonic X70 mobile phone (and maybe others e.g. GD87) on Linux using a reverse-engineered enhanced AT command set. It works in combination with a Linux bluetooth stack and should also work with phones connected by USB or serial devices.
xgsm is a Gnome-based GUI to the functions of the gsmlib library. With xgsm you can edit/backup/manage your mobile phone's phonebook and SMS entries. You can also send and receive SMS messages via your mobile phone using your computer.
xspeakfree is a Tcl/Tk (wish) frontend to Speak Freely.
Yate is a next-generation telephony engine; while currently focused on Voice over Internet Protocol (VoIP) and PSTN, its power lies in its ability to be easily extended. Voice, video, data and instant messaging can all be unified under Yate's flexible routing engine, maximizing communications efficiency and minimizing infrastructure costs for businesses.