A typical connection used to transmit/receive ARINC data might consist of a cable and a connector similar to the one shown below. Although ARINC transmit/receive channels aren't the only thing this interface can be used for. I've noticed that several different varieties of LRU also use some of the pin connections for I/O discretes. [![A typical connector used for ARINC signals.][1]][1] So, are the I/O discretes considered to be part of the ARINC interface? Or do they just coincidentally share the same connector and have nothing to do with ARINC? **Update** As one of the answers commented on... I am not talking about the discrete bits within an ARINC word but the physical discrete I/O voltage signals that you'd see on an avionics bus. [1]: https://i.sstatic.net/HnmeG.png