A visual seismogram drum-digitizer has been developed with precision adequate for the seismograms generated in standard networks. The variable speed, sampling interval and optical magnification permit convenient and efficient digital conversion of a wide range of record traces for different seismological research purposes.

An analysis of the precision has been made: over a dynamic range of 150 mm errors are less than 50 μ, and time intervals accurate to ±.05 sec for short-period seismograms or ±0.2 sec for long-period records.

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