This N Scale KA-N1 Keep-Alive(R) device has been specifically designed to be as physically small as possible. This product uses a slightly lower voltage and has a lower capacity compared to larger Keep Alive products such as the KA1, KA4, etc., and is intended to be used with N-scale decoders, such as the K7D4 and more! 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 KA-N1 can power an N-scale locomotive for 1-2 seconds over dirty track and power interruptions (depending on the number of lights and efficiency of the motor). The result is that if your locomotive loses electrical contact over a long switch frog or a short stretch of dirty track, it'll keep on running as though the problem didn't exist. The KA-N1 Keep-Alive device is part of the line of Train Control Systems N Scale decoders and accessories.