This video from oorail.com looks at the Train-Tech BL1 Red Buffer Light for OO and HO Gauge Model Railways. The BL1 has two red LEDs, for DC operation, the intensity is tied to the speed of the locomotive and one LED lights depending on the direction the train is traveling in. For DCC operation both lights will illuminate. The BL1 is very simple to install, the contacts clip to the inside of the rails. A very low cost but great addition to any layout.