... receiver and built-in geophone. Reflection and Refraction Exploration: Bedrock embedded depth, shape and regularities of distribution research, hydrological and engineering and ... Interval: 1 ms, 5 ms, 0 ms, three taps optional4 Preamplifier gain: 1, 32, 64 times optional5 Frequency ... One data file can be formed at each sampling, and every file contains the following texts: instrument number, station ...