Thanks for your post. I'm assuming the layer two protocol on these T1s is going to either PPP or Frame Relay? Basically what you need is a router with 4 T1 interfaces, so it can have a T1 connection to the internet as well as T1s to the 3 Netvanta 3448 routers. This can be done with the ATLAS but it isn't the recommended device. The ATLAS has some routing capabilities but is not a "router." You'll have to set up a PPP or Frame Relay endpoint for each connection. I suggest looking at the following guides: ATLAS PPP Endpoint Creation or How to Configure an Atlas for Frame Relay to an Internal Router
Once the links are set up, the ATLAS can route traffic between the 3448s and the internet, or even to the other 3448s depending on the destination address, but it cannot prioritize any of the IP traffic.
Hope this helps,
Thinking about this further, I don't believe the ATLAS will work for you at all. This is because even if you have a WAN IP address for the internet connection as well as a LAN block of IP addresses, the ATLAS won't allow the PPP (or Frame Relay) links to the NV 3448s to be on the same IP network. Each link has to be on a separate IP network. So unless you have a WAN IP address and 3 LAN networks, the ATLAS will not be able to "split" your internet connection.
By the way, each link will need at least a 30-bit subnet mask because the ATLAS will need an IP address and the NV3448 will also need an IP address.
Sorry for not catching this earlier,
Seems like an Adtran 4305 with an Octal T1 card would be a fit for this.
But as Patrick said -- depends on how you need to subnet / break up the feed from the ISP.
Why you would want to (or need to) do things this way seems worthy of more details if you'd like to supply them.
Since there has been no follow-up on this, I am going to mark it as "assumed answered." If you have additional information or questions please post it.