Michael McNamara writes on his blog:

If your in  pmshell  you’ll need to use the following escape sequences to get back to the “Connect to port >” prompt if for example you want to connect to different serial port. If you weren’t confused enough, if you are connecting via SSH you’ll need to use an extra ~ before those escape sequences so the ~ isn’t interpreted by your SSH client, it needs to pass through to  pmshell.

A handy guide to commands you might need on your awesome Opengear remote console box.

Read more: Opengear pmshell ESCAPE sequences