Scientific-atlanta, Inc.

Raheel Ahmed Khan

David B Burleson

William P Lafay

John T Filion

Donald Scott Cheek

An apparatus and method is provided for transmitting &ldquo;masked&rdquo; stereo audio signals in a signal distribution network such as a cable television system within the bandwidth constraints of conventional frequency allocation schemes. In various embodiments, left and right stereo audio signal components (L&plus;R and L&minus;R) are used to amplitude modulate a carrier using independent sideband (ISB) modulation without the transmission of a pilot signal. A jamming signal or low bandwidth data signal may be transmitted in place of the normal pilot tone. Various aspects of the invention contemplate the use of Hilbert transforms to perform the ISB modulation and demodulation.

Apparatus and method for masking audio signals in a signal distribution system

A communications terminal for receiving digital data services at a location remote from a transmitter comprises a service controller, a bus system, a random access memory and a non-volatile memory. The non-volatile memory preferably comprises FLASH memory. Data is first loaded into random access memory, preferably SRAM and there checked for errors and error-corrected. The data is preferably loaded in blocks into FLASH memory in a predetermined manner to further secure the service data and to permit the use of byte-wide memories accessed as word-wide memories. A service back-up memory is further connected to the bus for storing service data during suspension of play of a service. The service back-up memory preferably comprises a FLASH memory card having its own basic input output service (BIOS) control. A method of storing back-up service data in a home communications terminal comprises the steps of storing current service data in a first FLASH non-volatile memory and storing previous service data in a state in which play of the service is suspended is a second FLASH non-volatile memory, the service back-up memory described above.

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Lawrenceville, GA, United States of America

Raheel Ahmed Khan