_____________                    -
                |             |<---->              \            
                | Magic box   |<---->               \
                | with:       |<---->                \
    phone line  |             |<---->                 \
  --------------| D/A-A/D     |<----> 8 bit audio I/O  } bi-directional
  --------------| ring detect |<---->                  } printer port
                | ring/tip det|<---->                 /
                | latching    |<---->                /
                |  hook relay |                     /
                |             |-----> ring detect  /
                |             |<----- hook control/
                |_____________|                  -