If you have flipped through the 2 meter and 70 cm bands, you may have heard short burst of what sound like noise or modem tones. That's the sound of digital communications over the radio.
Digital communications allow our computers to talk to each other in a binary language.
Computers in the shack are now as much a part of the ham shack as the radio, coax or power supply. We use them for everything from plotting a satellite's location to computerized logging of QSO's. Sooner or later we want to transfer the file to someone else and when that time comes its easier to transfer that file by some form of digital communication. The only additional equipment that is needed is the device that breaks up the data and converts this into audio. This device is known as TNC or Terminal Node Controller.