Information on carrier.

Transmission of data - across distances but also between devices in system.
  Analog on analog:
    Radio - music and voice transmitted via radio waves.

    Telephone - voice using variable electrical currents.

    1G cell phones.

  Analog on digital:
    Music, movies on CD, DVD, Blu-ray  .

    On-line radio - analog data sampled.
 
    Long distance phone calls - digitally sampled, transmitted over fiber.

  Digital on analog:
    28K modems on computers, Internet via satellite.

  Digital on digital:
    Local area networks, fiber optics, high speed Internet.

  Newer cell phones:
    2G, 3G   
    Analog sampled to digital carried over an analog carrier(radio).