in order to verify the authenticity of the signature of an individual , first a sample signature is written with a pen which can generate electrical signals representative of the forces exerted in the plane of the paper in the process of writing . these signals are sampled and then scaled so that the signature when displayed , can be fitted within a predetermined display area . the scaled signals generated from the sample signature are then stored . when it is desired to compare the sample signature with a signature which is subsequently written , called a specimen signature , the specimen signature is written and is processed for display in the same manner as was the sample signature . the scaled sample signature signals are then called out of storage and displayed , as are the scaled signals generated in the course of writing the specimen signature . any deviations between the signatures are very readily detectable by observing the display .