A self-contained data acquisition unit is provided for acquiring seismic
data. The unit has a microprocessor and an antenna adapted to receive an
electromagnetic signal. A decoder is connected with the microprocessor
and adapted to convert received electromagnetic signals to dual-tone
multiple-frequency ("DTMF") digits. A geophone interface is provided with
a geophone for collecting acoustic data incident on the geophone. A
memory is connected with the geophone interface for storing a
representation of the collected acoustic data and for storing a
representation of a reference electromagnetic signal to be used in
synchronizing acoustic data collected by other data acquisition units. A
battery power source is connected with the microprocessor.