The RGB PAL Encoder Board

RGB PAL Encoder Board Photos

"This card is complementary to the normal Eurocard range, but also intended for general OEM use by the industry. It is an RGB-input PAL colour encoder with intercarrier sound, and was designed by Acorn for manufacture by Astec International. It is of particular interest to the Viewdata/Prestel industry for displaying high-quality colour graphics on a standard domestic television.

It accepts Red, Green, Blue and synchronisation signals and converts them to a composite PAL colour video signal; this is modulated onto a UHF carrier to produce an output on channel 36 suitable for feeding the aerial socket of a television. The board will also drive a monochrome TV to give a black and white picture, with the intermediate colours appearing as different levels of grey. The circuit includes a sound input, and the sound sub-carrier oscillator may be tuned to either 51/2MHz or 6.0MHz. Separate presets are provided for accurate setting of the spot frequencies for the colour and sound sub-carriers, should this be needed. The card operates from a single 5 volt supply, and is designed to fit a standard Eurocard rack.

The RGB PAL Encoder/UHF Modulator forms an ideal interface between the Acorn Teletext/Prestel VDU and a colour TV. Connection to the Acorn Teletext/ Prestel VDU is by an 8-way ribbon cable, which carries power as well as the signal lines. Note that Acorn provide a separate UHF PAL colour board for the Atom, and the two boards are not interchangable."

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