ATSC, SD and PC Card Input Signal FlowFigure 22The ATSC interface (DT board) processes the ATSC, NTSC, and QAM televisionsignals. It also processes the Photoviewer (JPEG) data of the SD and PC cards. Thecomposite, luminance and chrominance, or component video signals of the DT boardare output to the DG board via the connector DT12/DG22.The DT-Board has the ability to tune in the 8VSB ATSC terrestrial TV broadcast and the16VSB DVB cable television. If a cable line is used without a Cablecard, the unitproceeds to scan all available analog and digital channels. If a CableCard is used, thescanning process is bypassed since all cable related information is already programmedin the CableCard. If a terrestrial antenna is used, the unit may be instructed to scan onlyanalog or digital terrestrial broadcast. The unit may also be instructed to scan all analogand digital broadcast channels.The DT board contains an Optical Audio Out jack for use with a Dolby Digital decoderand a multi-channel amplifier. When a digital channel is selected, the output from theDigital Audio Out jack will be Dolby Digital. The same jack outputs PCM (Pulse CodeModulation) when any other signal source is selected.All TV related OSD information such as channel numbers, program channels, etc isgenerated within the DT board.As the OpenCable service changes, the firmware information located in the DT boardmay be upgraded through the use of an SD card. The Photoviewer SD card slot is usedfor the upgrade.27
