For anyone else who stumbles on this question, this is the method Topaz's documentation mentions here: https://www.topazsystems.com/software/download/sigweb.pdf

function IsSignaturePadConnected() {
    SetTabletComTest(false);
    SetTabletState(0, tmr);
    SetTabletComTest(true);

    if (tmr == null) {
        tmr = SetTabletState(1, ctx, 50);
    } else {
        SetTabletState(0, tmr);
        tmr = null;
        tmr = SetTabletState(1, ctx, 50);
    }
    if (GetTabletState() === '0') {
        //Cannot locate signature pad
        SetTabletState(0, tmr);
        SetTabletComTest(false);
        return false;
    } else {
        //Located signature pad
        SetTabletComTest(false);
        return true;
    }
}