I'm not sure whether you are serious, but that is indeed possible. There are routers with serial interfaces that can be connected to a dialup or leased line modem and there are even routers with dialup modems built in.
It is even possible (and very cheap) to use an old pc and build your own router (any flavor of linux or unix will do).
The SamKnows generic broadband router would be installed between the dialup router and your inhome network (which could just be a single computer). However I'm not sure if dialup users would be qualified for this test program.--
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