Hi guys, i need some help.
First of all my apologies for not being literate in the telco word and specially in voip questions. However i need to evaluate the feasibility of a project and time constraints do not allow me to properly educate myself! 
What we wanted to accomplish is to interface asterisk with a siemens hipath4000 pbx. The goal is to have asterisk route international calls via internet and leave all the rest to the siemens pbx.
Basically what i need to know is if this is doable? I know i can link asterisk to the siemens, but can i configure a topology so that all this is transparent to the end user? The Siemens is already in place and is not being replaced so it’s really a requirement that end-user impact is minimal!
Thanks for any help, Cheers.