With blue and a black w/ white stripe wire with which to attach it to a decoder.
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.
Newly-redesigned at half the size of a KA4, the KA2 will power HO or N scale locomotives with approximately one-third of the capacitance of KA3/KA4 devices (depending on the locomotive and motor).
Dimensions: 8.9mm x 8.9mm x 15.5mm
Scale: HO Scale N Scale
Input Rating: 12 to 16V