Retro-Geek: Acoustic Coupled Modem...

Demonstrating an early 300-baud acoustic-coupled modem.  When I first started messing around with microcomputers in the mid-1970s, one of my first acquisitions was an acoustic-coupled modem (a much later model than this one).  Their 300-baud speed was considered state-of-the-art, and I remember reading predicitions that the top-end theoretical speed was in the neighborhood of 700 baud (which a later direct-coupled modem from a company called PMMI actually acheived).  Here's the demonstration: