Maybe you can use the user_agent parameter. /Johan remo wrote: Hi all I have built the following 2 applications: - VoIP client for Windows Mobile phones - VoiP Softphone for PC Both apps work with the same SIP server. I am looking for a way for the SIP server to differentiate whether the SIP call is being originated from a mobile phone client or a PC softphone. Can anyone give an advice on this? Is there a good way to do this over SIP? I have a relationship to the SIP server developers so I can possibly ask them for changes on their side. Creative ideas are most welcome. Thx in advnace! Remo