Electronic circuit for a stenotype - guides the recording system in a stenotype with a position pickup having screening segment

摘要

This segment is connected with the recording system shaft. Phototransistors are illuminated through it by light emitting diodes, in order to apply opposite sense signals to a differential amplifier. These signals are subsequently compared in a comparator with input signals to the recording system. To compensate differential amplifier output signals variations due to temperature changes, a summary amplifier is connected through resistors to the differential amplifier output resistor. Its output is connected through a transistor collector to a series circuit consisting of the l.e.d.'s and their voltage source, so that the sum signal is kept constant by the l.e.d. current control. The l.e.d. material is gallium arsenide, and of phototransistors a silicon compound.