Fast optocoupler with high current transfer ratio.
Fully compatible with existing software, no additional drivers needed.
Wrong connection (input to input, output to output) is not dangerous to hardware, but obviously won't work.
Programs (usually games) sending MIDI messages directly to Amiga serial port, work with KA12 without any driver.
Programs accessing MIDI through camd.library do not need any drivers for KA12 as well. Serial port interface driver is embedded in camd.library.
The library is usually installed with MIDI applications, it may be also downloaded from Aminet.