dialling into my home broadband

I am on broadband cable, and would like a way to dial into it from my 56k modem when I’m within local calling distance, essentially, being my own temporary ISP.

I only have one phone line, is there a splitter or tone sensor that I can get to send modem signals to the modem, and phone signals to my phone?

Is there a router you know of that could handle this, or can windows 2000 do it?

thanks