Hi Nona,
This is Julie from Oregon, I am the Clearinghouse Manager here at Oregon State Police. The way we do it is through our dispatch center, which is a 24/7 unit. All AMBER requests go to them and they do the triage to see if they think it meets the criteria. If they think it meets the criteria, there is a list of sworn members that they call to get approval. They also call with denials and possible alerts to discuss what should be done. The final say comes from the sworn personnel assigned to the group. Everyone who is part of the AMBER Alert team understands that if their phone rings it could be an alert request, so they answer their phones at all times.
Hope that helps!