asterisk users - Apr 2006 - How can conference room can call out?

I have a group of local users. They want to participate on a conference 
call to a PSTN line in USA.
To connect they need to enter a code there as well.

I want to use a local conference room, where LAN users and local users 
can call in. The conference room should be connected to the conference 
abroad.

features.conf has:
[featuremap]
blindxfer => #1            ; Blind transfer
;disconnect => *0        ; Disconnect
automon => *1            ; One Touch Record
atxfer => *2            ; Attended transfer


Would this be a way?
1. First caller calls the USA number, keys in the code. BTW, the code 
includes a "#", I guess I should change blindxfer => ##, right?
2. transfer the call to the conference room:   *2789 (conference room 
789) and key in the conference room's password
3. all other participants log into the conference room (789)

Any thoughts, improvements for that ?


bye

Ronald Wiplinger