1. A system for authenticating a signature upon execution as with a writing instrument having a writing tip, comprising: a tablet means defining a surface for supporting a signature during execution, said tablet surface including discontinuities to form impulses when traversed by the forcefully applied tip of said writing instrument; electrical means for sensing said impulses to provide an electrical signature signal that is frequency related to the velocity of motion in the execution of said signature; signal-processing means for receiving said frequency related signature signal to provide a characteristic data signal for characterizing said signature; and means connected to receive said characteristic data signal to manifest an authenticity characteristic indicative of the authenticity of said signature.