Linksys Wireless Router :: How To Connect EA6500 To Phone Line

I just bought  an ea6500 to replace my old Billion router and up to now all I've had to do is plug my phone line directly into the "phone line in" port on the back of the billion router. But I see there is no "phone line in" port on the ea6500, I don't use a modem and have used the billion router by itself for the past 6 years, is there a way to connect my phone line directly to the ea6500 somehow? My research so far indicates you can't do it via an 'Ethernet / phone line adaptor' as they are incompatable anyway.
 
The install guide seems to expect a Modem is being used but in my case it hasn't been and I would think a router should perform the basic functions of a modem anyway ?
 
My concern is that if I really need to purchase a modem then won't this potentially 'throttle' the capabilities of the ea6500 which is the reason I've bought it in the first place ?
 
If I do need to purchase a modem to get my ea6500 working then what specs should I be looking for ??