There are two types of body waves: compressional (P) waves and shear (S) waves. Primary waves (P-waves) travel the fastest, so they arrive at the recording station (seismograph) first. Secondary or shear waves (S-waves) travel slower than P-waves so they arrive second.
Modified frequency modulation (MFM) is an encoding scheme used by PC floppy disk drives and older hard drives.
DTMF. (Dual Tone Multi-Frequency). DTMF is the global standard for audible tones that represent the digits on a phone keypad. With touch-tone land-line phones, pressing a key on the dialpad generates the corresponding DTMF tone for that key.