Which of the following is not an available I/O card for the System 6000?

In the context of the System 6000, it's essential to understand the available I/O card options to correctly identify which option is not part of the system. The System 6000 is equipped with a variety of I/O cards tailored for different audio interfaces and formats.

The Analog-4 card provides four channels of analog inputs and outputs, which is standard for many professional audio applications. The Digital-8 card offers eight channels of digital audio, catering to digital interconnectivity needs. The ADAT-8 card is designed for compatibility with ADAT interfaces, allowing for eight channels of ADAT optical input and output.

However, the Optical-8 card is not a recognized I/O card option within the System 6000 lineup. This indicates that while digital and optical connectivity is available through various means, the specific designation of "Optical-8" does not exist in the product's I/O card catalog. Understanding the distinctions between these available cards helps clarify the capabilities of the System 6000 and ensures proper configuration and usage for audio professionals.