ZBEEP doesn't work

[Han Pingtian <hanpt@xxxxxxxxxxxxxxxxxx>]

Hi,

I have tried to set ZBEEP to "\e[?5h\e[?5l" according to the manual, but
it doesn't make the terminal flashing. Because it's too quick the
reverse video on and off. If I run a command like this:

% print -b '\e[?5h';sleep 0.05;print -b '\e[?5l'

then there is a flashing on the screen. 

So what can I set in ZBEEP for a screen flashing?

Thanks.