367 / | HD | COMMUNICATIONS, ELECTRICAL: ACOUSTIC WAVE SYSTEMS AND DEVICES |
14 | DF | SEISMIC PROSPECTING {4} |
37 | DF | .~ Land-reflection type {6} |
38 | DF | .~.~ Signal analysis and/or correction {15} |
65 | DF | .~.~.~ Gain control {2} |
66 | .~.~.~.~ Analog/digital compatible systems |