Disabling root login

Hy,
Coud someone tell me how to disable root login via terminal (only from console should be allowed).
There is no ssh installed, only telnet.
I created a user which will have permission to su to root, but now i don't know where and what to modify to disable root login?

SCO OpenServer 5

Thanks in advance!

I believe this is set by editing /etc/default/login. Simply add the line:

CONSOLE=/dev/console