8.3 Multiplexed Analogue Components Transmissions

In the early 1980s Multiplexed Analogue Component (MAC) systems were developed as a transmission format that was more suited to satellite transmission. In Australia a variant of the MAC concept known as B-MAC was adopted for the HACBSS and RCTS remote area satellite broadcasting services.

The key features of the B-MAC signal format are:

• separation in time of the luminance and chrominance information;
• transmission of both luminance and chrominance as baseband signals;
• transmission of audio in a digital form in the line blanking period;
• transmission of vertical and line sync information as digital codes

As opposed to PAL, which uses a frequency division multiplexing method to combine the elements of the television signal, MAC systems use a time division multiplexing method.

The diagram below shows a typical MAC/packet television line (MAC/packet systems are also used in several European countries, they are very similar to B-MAC).

Figure 20: An example of the colour bar waveform of two lines of a MAC signal.

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