1ttyctl -fu
2       The -f option freezes the tty, and -u unfreezes  it.   When  the
3       tty  is  frozen, no changes made to the tty settings by external
4       programs will be honored by the shell, except for changes in the
5       size  of the screen; the shell will simply reset the settings to
6       their previous values as soon as each command exits or  is  sus-
7       pended.  Thus, stty and similar programs have no effect when the
8       tty is frozen.  Without options it reports whether the  terminal
9       is frozen or not.
10