var index_16_off = "images/index_16_off.gif";
var index_16_on = "images/index_16_on.gif";
var index_23_off = "images/index_23_off.gif";
var index_23_on = "images/index_23_on.gif";
var index_13_off = "images/index_13_off.gif";
var index_13_on = "images/index_13_on.gif";
var index_27_off = "images/index_27_off.gif";
var index_27_on = "images/index_27_on.gif";

function activate(imgName) {
	document.images[imgName].src = eval( imgName + "_on" );
}

function deactivate(imgName) {
	document.images[imgName].src = eval( imgName + "_off" );
}