TD6400 works similarly with TD6080, as zone decoder for PD Series of microphones with front manual zone selector. However some improvements are added to make this unit more flexible ie, it is divided into 2 groups of 4 zones each. This is useful in zone grouping setup when used with Matrix controller for zone expansion. It shall reduced the number of unused zones within the group.

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ie. if an output 1 from Matrix is to serve 3 zones ( zone 1 to 3 ) and output 2 with 4 zones ( Zone 4 to 7 ), only 1 zone shall be unused, as compared to using TD6080 which would have total 9 unused zones by using 2 nos of the unit.

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Starting zone address is now flexible and not tied up to the unit's starting address. Each group would have arbitrary starting address, such as group 1 with starting address of 9.

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TD6400 would be a perfect component to be used with Matrix controller for Zone Expansion, as illustrated in the diagram below.