If you need to use Skype or some other program for talking with computer, please ask to the sysadmin for the headset. Skype is installed on every linux workstation.

VoIP means Voice Over IP Protocol and it's just another acronim to indicate the possibility to use Internet like we use the phone: start the connection and talk with someone else in whatever part of the planet.

There's some technical difficulties that prevent this as the TCP/IP protocol wasn't designed to carry voice communications, but only data. today this difference is quite inexistent, but some difficulties remains for users withe reduced bandwidth. Until now the use of VoIP meant the necessity to install some program in out computer and start some strange sequence of operations to be able to connect with someone else. Fortunately now there's something standard and also stand alone device that work mainly like the phone at home. these phones are like computers, but they can do only one thing: permit to you to talk to someone else.

At the moment there's 2 different standards mainly used by these devices and also by programs running on standard computers: Skype and S.I.P.

Skype is the first program that really had a spread diffusion and that permitted to lot of people to start talking communications. It's based on a standard proprietary that is an evolution of the former Kazaa protocol, used for the peer 2 peer sharing files. This program and the protocol is a “de facto” standard and is used by millions of computer's users. Using a program or a phone device that support this protocol, you can talk with someone else for free or spending very little. In order to use Skype, you have to subscribe to the service and you'll receive a nickname that can be used by others to call you. Normally all the participants to a communications (you can start also conferences with 4 or more listeners/talkers) must be subscribed to skype, but you can also call and be called from normal lines numbers, if you're subscribed to the extension of the service (charged). To use skype, start the program you'll find under the “Application→Internet→Skype” voice, insert your account information and configure the audio devices (if needed) to be used. With Linux the configurations of audio devices can be a little difficult, there's too much possibilities. the major part of the problems are generated by the mic, that is not used by default on Linux audio configurations.
In order to configure correctly the mic device:

1. Start the program alsamixer from a terminal using the command alsamixer -c 0 [enter].
2. Press the TAB key one time to reach the Capture section.
3. Check that the “CAPTUR” voice is active in all the “Mic” column. If the voice is somewhere else, move the cursor under the “Mic” voice and press the space-bar until the voice is activated.
4. Now move on the “Playback” section using the TAB key (the section selected is displayed in the upper part of the terminal window)
5. If it exist, check that the “Mic Boost” is activated. if you see the voice “MM” inside the block, the mic boost is deactivated. press the M key to activate it.
6. Move to the “Mic Sele” column and using the space-bar cicle through the different mic devices you have. Between every change test the device with skype, if you can hear yourself the configuration is done.
7. Close the alsamixer program pressing the Esc key.

On Skype you have to configure the audio devices (on the preferences panel) this way:

• Sound In: should be the first hardware device listed. normally is indicated as (hw:intel,0). if this doesn't work, try the others one listed.
• Sound Out: pulse
• Ringing: pulse

Pulseaudio, the daemon that manage the audio card sometime hangs. In this case you must close all the program that use the audio device and restart the daemon. most of the times, the crash of pulseaudio is caused by Flash animations. to stop/start the pulseaudio daemon, from a terminal launch these commands:

 pulseaudio --kill
 pulseaudio --start

the daemon will stop and restart. Then you can reopen he applications that you closd before.

S.I.P. is the standard “de jure”, it's the specification that all providers and producers of VoIP devices must follow in order to generate a “compatible” device that can interconnect with others device on the Internet. The S.I.P. protocol is well supported where there's large bandwidth, but differently from skype is not always usable free of charge. other difference whit Skype is the fact that you use SIP phone mainly to connect to the standard voice line and you can also receive a standard telephone number from the provider where you subscribed.
In the major part of the occasion you can receive the communication for free, but if you want to call someone you have to pay a subscription. Almost in every case the subscription is less costly that the one you have using your standard voice line/phone.