Console/Telnet/SSH into the switch with proper credential and then run “_cmdline-mode on”.
The switch will prompt you a YES/NO question, just type in YES.
Then switch will ask you for a password. If you did not have the password, just type in “512900”
From now on, if you do question mark or run “system-view”, there will be more commands available.
PS. if you use putty for connection, try to use “Ctrl+h” as Backspace key for HP/3Com switches.