These were interlocking signals, as evidenced by the dual heads, and the switch was controlled by the operator at Monon. Never having worked the north end, I don't know the exact indications a train could get from this signal, but if both units were red, it would have been a stop indication. A S/B train staying on the main track would get a green or yellow over red, and a train headed down the Indianapolis line would get a red over either a green, yellow or white. I have attached a copy of Rule 290 from the last Monon rule book that shows some of what the signal could have displayed, with further instructions governing it's use being shown in other rules or Timetable special instructions. Hope this helps. / Ron
