In which DTMF means "Dual Tone, Multiple Frequency"
The range of modern SDR devices covers broad frequencies including Aviation and Marine tracking, decoding Trunked radio systems, downloading Weather Satellite images, reversing wireless protocols, hunting for Numbers Stations, or even watch the International Space Station broadcast Slow-scan TV
Eavesdropping on the Hidden World is endotoxin's excellent first post about the changes in tech and requirements that have led to a renaissance of scanning and ham radio, with many interesting tips from members in the comments.