The invention is directed to techniques for monitoring organ rejection. In a first embodiment, the vibration detector comprises a support member arranged to vibrate, and a sensor arranged to detect a vibration frequency of the support member. The service provider compares the content usage fee in the received usage log with a predetermined threshold. The resulting uncompressed pixel data matches or closely resembles the video data prior to compression and storage. Synchronization is implemented using file locks enforced by the file system, so there is no need for a master synchronization process. The control electrodes are coupled to the common terminal via a third controllable semiconductor element.