Hello,
Check than you use a null modem cable.
If you are running AIX 5.3, you can chek the tty parameters
lsattr -El tty(0) and complete the parameters "logmodes and runmodes". This is necessery with AIX 5.3. You sohould had th "clocal" parameter.
logmodes
hupcl,cread,echoe,cs8,clocal
runmodes hupcl,cread,brkint,icrnl,opost,tab3,onlcr,isig,icanon,echo,echoe,echok,echoctl,echoke,imaxbel,iexten,clocal