MADI
Multichannel Audio Digital Interface — 64 audio channels down a single coaxial cable, standardised as AES10 in 1991.
Where AES3 carries two channels per cable, large studios and broadcasters needed something to replace thick analogue multicores. MADI was developed by Solid State Logic, Sony, Neve and Mitsubishi and carries 56 or 64 channels at 48 kHz over 75-ohm coax with BNC connectors (around 100 metres) or optical fibre (a couple of kilometres). At double sample rates the channel count halves.
Each link is one-way, so full duplex takes two cables, and clocking usually comes from a separate word clock. It is boringly robust and survives in broadcast and live sound, even though networked systems like Dante have taken over new installs. Its eight-channel prosumer cousin is ADAT.