If you are using a SIP account to call or maybe have a own Asterisk server, you might want to use Sipdroid. Sipdroid is a SIP softphone for your Android mobile phone or tablet. Using SIP could decrease your telephone costs if used properly :-). Well let see how to configure Sipdroid.

1. Install the application "Sipdroid" from the Android Market.
2. Open Sipdroid and press the menu button of your phone.
3. Choose "Settings".
4. Click on "SIP Account (Line 1)"
5. Click on "Authorization username" and enter your extension number here for example “1000”, without the “ ofcourse.
6. Enter your SIP password into the option "Password"
7. Also enter the option "Server or Proxy". Please enter the IP or hostname of the SIP (Asterisk) server.
8. As for protocol, please select "UDP".
9. Also check the option "Use WLAN". This tells Sipdroid to enable on wifi connect of your phone. If you like you can also check the options "Use 3G" and "Use EDGE", but if you do please make sure that this will not give you extra costs.
10. Then go back to the main screen of your settings (where you see SIP account, Call option etc).
11. Choose for "Call options".
12. Choose for "Preferred Call Type" and select "Always ask". This setting will now make sure that when you make a call it ask if you want to route it as normal phone call or handle it trough your SIP account.
13. You are now ready to make SIP calls. If the audio isn't great, you can play with the Audio options. Also there is a feature called "Improve audio" in the setting "PBXes features".

I also noticed that the audio of Sipdroid can be improved if you use the G722 codec of Sipdroid. This codec will only work if you SIP provider allows you to. But you can always try and set this setting. You can do this from the main settings page of Sipdroid, choose for "Audio Codecs" and change the setting of "G722 HD Voice" to always try.