Yes. On the aux line, configure
"trans input all", then telnet to
the IP address of the 1720 with a
port of 200X, where X is the line number
of the aux port. So, for example
telnet 1.1.1.1 2001 would connect to
line 1.
If the router is a access server, then
the X will be the number of tty lines present
plus one.