A fault-tolerant virtualized computer system comprises a primary host executing a primary virtual machine and a backup host executing a backup VM. The method includes multiplexing a first digital video sequence with a second digital video sequence, pictures of the second digital video sequence are included in advance in a video stream and are associated with timing information such that a receiver will not decode and reproduce the pictures of the second digital video sequence. A relation between temperatures of the respective portions on the heat treatment table and temperatures detected by the sensors is grasped in advance, thereby enables to surmise a temperature of the respective portion of the heat treatment table from the temperature detected by the sensors. Account representatives are given access to the suspended numbers. To address the potential conflict, each server will implement a back-off strategy for negotiating which server will actually process the work request. The second enclosure has all electronics, controls and a battery compartment.