Digital communications is becoming more and more efficient. It began with morse code many years ago and has now become a mode of great importance. Not only does digital communications offer faster communications, but it has become increasingly more efficient. RTTY (Radio TeleTYpe) uses an audio tone that switches between two different frequencies, somewhat similar to the dahs and dits of morse code. RTTY makes use of single sideband, and is therefore an audio-application. That is, when you are using RTTY, you are using an audio signal (it is mixed into an SSB signal the exact same way that a voice is). By rapidly switching between two audio tones, words can be created. Usually the tones are about 170 Hz apart, so the bandwidth of RTTY, even though it is a single sideband application, is quite small. Other methods of digital communications have been developed that have error checking and correcting built into the software that runs these machines. Packet is one such method that has error correction built in. Without error correction, words can become jumbled by the uncertainties of propagation on the HF bands, which RTTY is usually confined to. GTOR, PacTOR, CLOVER and a host of other methods other than packet and RTTY exist. As time permits, I will include more general information about all of the methods.