var menu_name = new Array(4);
menu_name[0]="o";
menu_name[1]="r";
menu_name[2]="s";
menu_name[3]="h";
var img_tower_lg  = new Array(4);
var i;
for (i = 0; i < 4; i ++) {
    img_tower_lg[i]      = new Image();
    img_tower_lg[i].src  = "./images/contents_body_tower_" + menu_name[i] + ".gif";
}

function tower_images_on(menu_id) {
	var n = menu_id.charAt(4);
	document.images["towerLg"].src = img_tower_lg[n].src;
}

function tower_images_off() {
	document.images["towerLg"].src = "./images/contents_body_tower.gif";
}