Abstract: Apparatus is provided for determining the conformity of an energy pulse generated by a weight drop seismic source to a defined energy pulse characteristic in order that reflections associated with a non-conforming energy pulse can be rejected. The apparatus operates to compare the signature of a weight drop with a signature standard. Incoming seismic data is rejected and not recorded if the difference between the incoming signature pulse shape and the standard signature pulse shape is too great. The pulse shape of the incoming signature is analyzed by comparing a sample of the incoming signature amplitude to upper and lower rejection limits derived from a time correlated amplitude sample of the standard signature. The upper and lower rejection limits against which an incoming signature sample is compared are proportional to the amplitude of the time correlated standard signature sample.