I am guessing that phase 1 approval is the completion of review by the service centre (?). The paperwork is then passed onto the NVC who process it next. The visa fee bill is then requested ( about 4-6 weeks after you are entered into the NVC system ), once this is received by the NVC they will then generate packet 3, which contains the DS230 and some other papers. This is then reviewed by the NVC, once this is complete ( in my case 7 days ), the papers are then sent to whatever consulate you chose. Depending on what consulate you are using, there is now a wait for an interview ( in my case 60-90 days), I am waiting to receive packet 4, which contains info about police clearances, medicals etc.
Just as an idea of time- my case was created by the NVC on Nov 2 2004, completed on March 16 2005, sent to Sydney on Mar 22 ( and is still enroute!)
Hope this has been of some use to you!
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