Abstract: A power supply for a satellite receiver system includes a dual input supply voltage arrangement. When a higher output voltage is selected, a source of a lower supply input voltage is coupled to an input main current conducting terminal of a series pass transistor. On the other hand, when a lower output voltage is selected, a source of a lower supply input voltage is coupled to the input main current conducting terminal of the series pass transistor. A comparator senses a magnitude of an output voltage produced by the series pass transistor. When, as a result of an over current condition, the output voltage is lower than a reference threshold level, any selection of the higher output voltage is automatically overridden and the source of the lower supply input voltage, instead, is coupled to the input main current conducting terminal of the series pass transistor.

Abstract: Hacking of a class of Set-Top Boxes known as Integrated Receiver-Decoders (IRDs) used to receive satellite broadcasts for display on television sets is prevented by use of connections to the reprogramming enable pin of a flash memory. If a user attempts to reprogram the boot sector of the flash memory in order to obtain free service via privacy, the set-top box is destroyed. The invention relates to the design and manufacture of IRDs that are resistant to hacking via unauthorized reprogramming.