function active(imgName) {
    if (document.images) {
        document[imgName].src = eval(imgName + 'ON.src');
    }
}

function activeFront(imgName) {
    if (document.images) {
        document[imgName].src = eval(imgName + 'FR.src');
    }
}

function activeBack(imgName) {
    if (document.images) {
        document[imgName].src = eval(imgName + 'BK.src');
    }
}

function inactive(imgName) {
    if (document.images) {
        document[imgName].src = eval(imgName + 'OFF.src');
    }
}