how to check node type in page-forum.tpl.php file

[feelexit]

I am using drupal 5.6

in page-forum.tpl.php file, i try to
<? if ($node->type == 'forum') { echo "forum"; } ?> , I didnt get "forum" .

then I use print_r to print out $node array. find out $node is empty. why is that ? if i cannot use $node, what other variable i can use to check if I am in the forum page.