Common codecs between Ekiga en X-lite

As recommended on the TrixBox.org fora, we try to limit the codecs set to the common ones. to do so, we register Ekiga as a SIP phone to the TrixBox and make a call; the Ekiga log shows then the following:

10:07:42 Started Ekiga 2.0.3 for user fabio
10:07:47 Registered to 129.125.21.241
10:07:57 Call from Anneke SIP freePBX
10:07:59 Answering incoming call
10:08:00 Opened Intel ICH5 for recording with plugin ALSA
10:08:00 Opened codec PCMU for transmission
10:08:00 Opened Intel ICH5 for playing with plugin ALSA
10:08:00 Opened codec PCMU for reception
10:08:00 Connected with Anneke SIP freePBX using Asterisk PBX
10:08:10 Closed codec PCMU which was opened for transmission
10:08:10 Closed codec PCMU which was opened for reception
10:08:11 Local user cleared the call 

The X-Lite unluckily doesn't report any codec information.

From this log we can conclude that the used codec is the Ekiga's PCMU, which is likely to be X-Lite's G711u.