Apparatus and instruments for use in seismic exploration, seismic protection and related diagnostics and monitoring, namely, seismographs, seismometers, seismic detectors, seismic exploration machines and apparatus, seismic vibrators, geophones, hydrophones, electrical transducers, electromagnetic transducers, pressure transducers that convert hydraulic, pneumatic, seismic and earth pressure into analog electrical signals, electrical components in the nature of analogue filters, signal conver...