This series has a stereo digital audio subsystem for passage. It has 4 channels, with a resolution of 8 bits each. The module that generates and transmits these channels is in the Central Rack.
Each seat has a receiver module that receives the 4 audio channels, and decodes and sends them to the seat connection panel. Depending on whether the seat is Tourist class or First class the model changes, although the functionality is always the same.
Each module incorporates a self-test function, so that when the Central Rack orders it, each receiving module verifies its correct operation, indicating its status.
The module that generates the four channels of digital audio is in the Central Rack.