The basic principle of working is to enable a programmable key in any IP phone that will play a DTMF tone. This tone will automatically create a dynamic conference room and add the caller and the called number to this conference room. If the extension receives or makes a call in a second line appearance and presses the conference button (DTMF tones) again, this incoming call will be added. If any of the participants make or receive a call and the conference button is pressed again, this call will be transferred to the conference room, and so forth. There is no limit to the number of participants in the conference room, and this key could be configured for all devices. This feature is based on the working principle described on the following web page:

http://www.voip-info.org/wiki/view/Asterisk+n-way+call+HOWTO