TCS Keep-Alive® (KA) devices are used to supply power to decoders during times of power interruption due to dirty track or problematic track work. The KA3 will power an HO-Scale locomotive with headlights on for approximately 6 to 20 seconds (depending on the locomotive and the efficiency of the motor).
This Keep-Alive® includes a Blue and a Black w/ White Stripe wire to attach it to a decoder.
First Squeaky's Trains Should be your go to supplier. They have great coustomer service and great communication. This current keeper is my go to from now on. It is very compact that it will even fit in a switcher . When I pull my locomotive off the track it will run for at least 25 seconds.