The Train Control Systems KA4-P Keep-Alive® is a compact stay-alive capacitor pack that feeds backup power to your DCC decoder whenever the wheels lose contact with the rails. No more stalling on dirty track, dead frogs, or insulated turnouts — the KA4-P keeps a locomotive running with its lights and sound on for roughly 6 to 20 seconds during a power interruption, depending on the locomotive and motor efficiency.
This is the harness-equipped version: it ships with a 2-Pin Quick Connector Harness that plugs straight into any decoder with a compatible 2-pin Keep-Alive socket, such as the TCS T4 and other current TCS decoders — no soldering to the decoder required. Electrically it works in any scale, and its tiny .52" footprint tucks easily into HO and larger locomotives.
Browse more decoder add-ons in our DCC Accessories collection, shop the full Train Control Systems lineup, or pair it with a new sound decoder from our DCC Decoders collection.
What does a Keep-Alive actually do?
It stores an electrical charge and feeds it to your decoder when track power drops out, so the locomotive keeps moving and its lights and sound stay on across dirty track, frogs, and gaps.
Will the KA4-P plug into my decoder?
The included 2-pin harness plugs into TCS decoders with a compatible Keep-Alive socket (such as the T4) and most current TCS decoders. For decoders without a 2-pin socket, you can solder the leads to the decoder's keep-alive pads — check your decoder's manual first.
What scales can use it?
Electrically it works in any scale. Its small size suits HO and larger; in N scale it fits wherever there is room in the shell or tender.
How long will it keep my loco running?
Expect roughly 6 to 20 seconds with headlights on for a typical HO locomotive, depending on motor efficiency and current draw.
