Different polling rates are applied to high priority BE service flows depending on whether the service flow contains, or is about to contain, traffic packets. The multichannel-type radio frequency modulation circuit is configured in a multichannel modulation manner in the set-top box such that a plurality of televisions receive broadcasting signals at different channels via the radio frequency modulation circuit. The output queue stores packet pointers to data to be transmitted to the egress port. For discontinuous mode of operation of the power converter a pulse averaging sliding mode control is being used. In this way, the inflow valve assists in increasing the magnitude and duration of negative intrathoracic pressure during decompression to enhance the amount of blood flow into the heart and lungs.