Electrical writing pen and sensor

Claim 1

An information transmission system including a writing instrument for detecting the information to be transmitted and a writing table with associated electronic circuitry having positions represented by time varying electrostatic field components, said writing instrument comprising, in combination: a. a pen cartridge containing ink and including a pen point at one end thereof for transferring said ink to a writing surface for effecting a visual record of the path of said pen point; b. a pen cartridge housing having a longitudinally extending cavity for receiving and supporting said pen cartridge in said housing with said pen point extending from said housing; c. an electrostatic field pick up element forming a part of said pen point for detecting and re-radiating said electrostatic field components in proximity to the point of contact between said pen point and said writing table; d. an electrostatic field sensing element secured in said housing adjacent said pen point of said pen cartridge for detecting said electrostatic field components radiated by said pick up element and issuing an output signal in response thereto; e. signal amplifying means secured to said pen cartridge housing at an end remote from said pen point; f. electrical conducting means extending uninterrupted substantially the length of said housing and connected to said field sensing element and to said signal amplifying means; and g. means defining an opening in said cartridge housing extending longitudinally thereof and communicating with said cavity to permit said pen cartridge to be removed and replaced without disconnecting said electrical conducting means.