I want to make the simplest and most reliable on/off device controlled from a compuer software (Java).
I was thinking about sinus sound singnal + RC filter with relay for specific frequency, but unfortunatelly I can't use sound card - it is already occupied for different purposes.
How can I achieve this without much compatibility/reliability issues. It should work both on Unix and Windows
I mean an output device, so I want to turn on/off relay from Java software.
USB MIDI adapter and then midi to relay .