Apparatus in an earth bore logging system for restoring two or more closely occuring pulses which have become distorted through transmission from subsurface equipment to the surface to the extent that such pulses tend to merge into a single pulse of longer duration. Each pulse from the subsurface signal source is extended in duration to a predetermined pulse width when widely separated from adjacent pulses, and is extended to a greater extent when a successive pulse occurs during the predetermined pulse width period. The pulses are then transmitted to the surface where such extended pulses are amplitude normalized. Each normalized received pulse at the surface is used to generate a pulse having a duration proportional to the duration at which the amplitude of the normalized pulse exceeds a given level. Each of the trigger pulses in turn results in the production of a reference pulse terminating after termination of a trigger pulse of normal duration, representative of a single pulse before transmission. A first output pulse is generated in response to one of the trigger and reference pulses and a second output pulse is generated only upon time coincidence of the trigger pulse and termination of the reference pulse. The widths of the reference pulses may be automatically adjusted according to variations in the average widths of the trigger pulses.