I have put together an "Audio band network" where audio cables from the sound card of a laptop are distributed to a classroom full of similar laptops.
The wires substitute for radios allowing many users to talk to each other. It works well for teaching FLDIGI and many other digital modes and protocols where each station is independent. Details are available for the asking.
The machine KB2PCN-5 resides on is suddenly having power supply issues. (Not backup/UPS power issues; something to do with the onboard psu.) - This is remote and it'll take me a bit to get to it; so expect intermittency until I'm able to repair/replace the machine in the next two weeks or so.