vi设置了expandtab时，如何插入制表符

vi设置了expandtab时，如何插入制表符
:help et

'expandtab' 'et'        boolean (default off)
                        local to buffer
                        {not in Vi}
        In Insert mode: Use the appropriate number of spaces to insert a
        <Tab>.  Spaces are used in indents with the '>' and '<' commands and
        when 'autoindent' is on.  To insert a real tab when 'expandtab' is
        on, use CTRL-V<Tab>.  See also :retab and ins-expandtab.
        NOTE: This option is reset when 'compatible' is set.