GRAFISKT BORD, SERSKILT FOR ETT TELESKRIFTSYSTEM

摘要

A graphics table comprises a non-conductive plate supporting two crossing layers of wires and a pen for writing on a sheet disposed on the plate. The wires are successively scanned by an electric current which creates a field to be detected by the pen. The electric current has a high frequency, for example of the order of ten megahertz, and the wires are switched at a frequency of for example one hundred kilohertz. The pen is followed by a selective amplifier of ten megahertz, by a filter, by a detector, and by a circuit for determining the time when the picked up signal passes through a peak. The invention is notably useful in a telewriting system.