Adding signal detection to rolling stock

摘要

After spending the time wiring an operating signal system, you want to be sure that it can "see" all your rolling stock or else you could have a clear block full of freight cars. Most signal systems rely on occupancy detectors that sense current draw, such as that from a powered locomotive or lighted coach. For a car that doesn't draw any current, you'll need to add resistors to a couple of its wheelsets. With the surface-mount-technology (SMT) chip resistors available today, it's easy and inexpensive to equip your entire rolling stock fleet. Chip or SMT resistors come in the same values as old-fashioned axial-lead resistors but take up a fraction of the space and have electrodes instead of leads. Each chip resistor that I use for my HO wheelsets is about the size of a pencil tip and costs a penny.