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

EIA-422

RS-422 is a technical standard that specifies electrical characteristics of a digital signalling circuit. Differential-mode signals can be sent at rates as high as 10 million bits per second, or may be sent on cables as long as 1200 metres. Some systems directly interconnect using RS 422 signals,...

. 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

Data transmission

Data transmission, digital transmission, or digital communications is the physical transfer of data over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibres, wireless communication channels, and storage media...

 bus. Data is transmitted over an interconnecting cable by devices that comply with Electronic Industries Association (EIA) RS-422A

EIA-422

RS-422 is a technical standard that specifies electrical characteristics of a digital signalling circuit. Differential-mode signals can be sent at rates as high as 10 million bits per second, or may be sent on cables as long as 1200 metres. Some systems directly interconnect using RS 422 signals,...

.