The Commercial Standard Digital Bus (CSDB) is a unidirectional asynchronous bus, formerly known as the Collins Standard Digital Bus. The physical layer is EIA-422. The maximum speed is 50 kbit/s. It is used on most buses in NSW.
The Commercial Standard Digital Bus is a two-wire asynchronous broadcast data transmission bus. Data is transmitted over an interconnecting cable by devices that comply with Electronic Industries Association (EIA) RS-422A.
References
Commercial Standard Digital Bus Wikipedia(Text) CC BY-SA