First of all you need some kind of CSU/DSU to terminate the T1. That said most devices I've seen have router functions built-in. Theoretically you can use your Linksys for any WAN device so long as that device egress with 10/100baseT Ethernet. But if you have a T1 router then it defeats the purpose of using the Linksys. Furthermore, you may have difficulties if your T1 is a nailed PPP connection since the Linksys uses PPPoE for authentication. I doubt you would be using PPPoE over a T1, but I could be wrong about that.