A crossed-slot antenna is fabricated using rectangular sheet of metal. A monitoring mechanism determines if the minimum filling level of the playout buffer over a time period whereby the average filling level of the playout buffer is reduced according to the minimum filling level of the playout buffer over the time period. In preferred embodiments, the systems and methods described herein can be embodied in catheterization systems. When the unique locating reference for the data object is received, controlled access to the data object and the snapshot is provided. The milling apparatus includes a chamber having a rotary milling head located in it.