How to connect two NT server 4 through 9

I have two Office nearly about 2Km appart from eachother. On both office i have installed NT server 4.0, with RRAS on both site, DHCP also installed on both site.
I want to connect both server hrough 9.6 kbps hotline. HOW?
Which Instruments needed?
I can able to connect both nt server through normal Dial up line with modems.