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            tuon.src = "images/r_4.gif";   
 
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            tuoff.src = "images/r_1.gif"; 
        }
 
function tuOn(imgName) {
        if (document.images) {
            document[imgName].src = eval("tuon.src");
        }
}
function tuOff(imgName) {
        if (document.images) {
            document[imgName].src = eval("tuoff.src");
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}
//-->