Two-conductor bidirectional digital seismic telemetry interface

The invention relates generally to seismic prospecting and, more specifically, to telemetry between a master electronics module, such as a data collector, and one or more slave electronics modules, such as seismic sensor data acquisition modules. A two-conductor bidirectional digital telemetry interface between a seismic sensor acquisition/conversion module and a seismic data collection module. The data collection module is configured as a master electronics device and the sensor acquisition/conversion module is configured as a slave electronics device in the telemetry system. The master device provides power to the slave device over the two conductors. The master device transmits portions of commands to the slave device at a first time and the slave device transmits portions of a digital seismic data packet to the master at a different second time in a fixed-duration frame. The frames are transmitted at regular intervals. The outbound commands and inbound data are encoded by block codes. A phase-locked loop in the slave is locked to a master clock in the master by deriving a clock and a sync point from the block-coded commands it receives from the master. The block code representing each command bit minimizes dc drift and provides a level transition in the command that can be used to maintain synchronism between master and slave.