Data buses:

The availability of reliable digital semi-conductor technology has enabled the inter-communication task between different equipment to be significantly improved. Previously, large amounts of aircraft wiring were required to connect each signal with all the other equipment. As systems became more complex and more integrated so this problem was aggravated. Digital data transmission techniques use links, which send streams of digital data between equipment. These data links may only comprise two or four wires and therefore the inter-connecting wiring is very much reduced. Recognition of the advantages offered by digital data transmission has led to standardization in both civil and military fields. The most widely used digital data transmission standards are ARINC 429 for civil and MIL-STD-1553B for military systems.

AERONAUTICAL RADIO INCORPORATED (ARINC) 429

ARINC specification 429 is titled "MARK 33 Digital Information Transfer System" (DITS). We refer to it as ARINC 429 bus, DITS bus, Mark 33 bus or just ‘bus'.

An equipment transmits data, via a 429 transmitter, to other equipment. The information flow is uni-directional. One 429 transmitter supplies the data to a pair of wires that we call the bus. One or more ARINC 429 receivers can be connected to the bus.

The ARINC 429 bus is a twisted and shielded pair of wires and the shield is connected to ground. The data wires are white and blue. The ground connection is a black wire. If the bus runs through a feed-through plug (for instance on a bulkhead), then the shield is also connected to a black wire that runs through the plug.