Abstract: A system for recording input electrical signals by positioning galvanometer pen styli relative to a chart paper device in accordance with the input signals. Each pen is mechanically linked to an optical mask. The optical mask in conjunction with an optical system provides a feedback light signal, which is converted to a feedback electrical signal for nulling the input signal. The ink application device includes structure for applying pressure directly to carbon paper, which in turn transfers the carbon or ink to the chart paper, thereby recording clear representations of the electrical signals.