This recording equipment is undoubtedly the first of its kind. It is a battery-powered system with a separate two-wire circuit to each station. A signal coming from one of the tour stations activates the corresponding solenoid, which drives its pin to prick or puncture the back of the chart, acting against a strike bar at the front of the chart.

To the left, the strike bar, reflected in the chrome plate. Each solenoid, when activated, punches through the paper chart, hitting the cupped end of the corresponding target screw. The targets are adjustable for optimum performance without letting the solenoids stick in the paper.