JQuery Two 'Select All' Checkboxes Across 2 Tables

I have two tables that are filled with a number of checkboxes (the number is variable based on a retrieval profile defined on a previous screen). I've implemented a Select All check box at the top of each table with the following:

    $('#select_all').bind('click', function() {
    if(this.checked) {
        $(':checkbox').each(function() {
            this.checked = true;
        });
    } else {
        $(':checkbox').each(function() {
            this.checked = false;
        });
    }
 });

But this function selects all checkboxes in both tables (as it is poorly written to do). Is there an easy method of having the code select all checkboxes in each distinct tables.

Thanks.