how to pass values of unchecked boxes only?

I am working on html form where i have number of checkboxes but i want to pass only unchcked values to other form (get_value.php).

   <form action="get_value.php" method="post">
    <input type='checkbox' name='products[]' value='call1'>col1<br>
    <input type='checkbox' name='products[]' value='call2'>col2<br>
    <input type='checkbox' name='products[]' value='call3'>col3<br>
    <input type='checkbox' name='products[]' value='call4'>col4<br>
    <input type='submit'  value='Submit'>
    </form>

Is there any way to filter $_POST['products'] to get uncheked value only?