I’ve trolled the internet looking for ways to configure the v92 modem on a cisco 1811, and have managed to paste together pieces to make a dialup connection from the router, please note this configuration will not work with the aux port.
interface Async1
no ip address
ip nat outside
ip virtual-reassembly
encapsulation ppp
no ip route-cache cef
no ip route-cache
dialer in-band
dialer pool-member 1
dialer-group 1
async mode interactive
!
interface Dialer0
ip address negotiated
ip nat outside
ip virtual-reassembly
encapsulation ppp
no ip route-cache cef
no ip route-cache
dialer pool 1
dialer remote-name ***ISP NAME***
dialer idle-timeout 2000
dialer string ***NUMBER***
dialer hold-queue 10
dialer-group 1
no peer default ip address
ppp authentication pap chap callin
ppp chap hostname ***USERNAME***
ppp chap password 0 ***PASSWORD***
!

Dialer profiles separate logical configurations from the physical interfaces that receive or make calls. Because of this separation, interfaces such as ISDN, asynchronous modems, or synchronous serial connections can be shared by multiple dialer profile configurations.