The trucks with RR wheels are called HI RAIL trucks. Most RR signal systems operate on batteries with charger. UP has a light on the outside of their signal cabinets that indicates AC power. Many have strobes that operate when power fails telling train crews so they can radio a signal maintainer. The old signal systems had glass jar batteries, most have been replaced by gel batteries. Newer signaling systems are less power hungry than older systems due to solid state controls. Robert
