Afraid not - you always need login details for the sip connection - these are usually as simple as a username, password and sip phone server but every site will be different.
However, you could setup a sip account from an online provider like voip.co.uk and then as long as you have a good internet connection you will connect that way each time from anywhere on earth.
Peter Jarrett, Technical Director
Broadcast Radio Ltd.
Bill Bailey: No win, no fee, no basis in reality. Just a room above a minicab office in Acton and a steady stream of greedy simpletons whose delusion is only matched by their clumsiness