protected void rmBus (Object busname)
        {
            USB  bus = (USB) busses.get (busname);

            if (bus != null) {
                if (trace)
                    System.err.println ("rmBus " + bus);

                for (int i = 0; i < listeners.size (); i++) {
                    USBListener listener;
                    listener = (USBListener) listeners.elementAt (i);
                    try {
                        listener.busRemoved (bus);
                    } catch (Exception e) {
                        e.printStackTrace ();
                    }
                }

                busses.remove (busname);
                bus.kill ();
            } else {
                if (trace)
                    System.err.println ("rmBus: could not find named bus to remove " + busname);
            }
        }