DCC ‘Stay Alive’ and what it means

One of the most important features of Digital Command Control (DCC) systems is the constant supply of power to the track, writes Nigel Burkin.

Unlike traditional analogue control systems, by which trains are controlled by controlling the level of power supplied to the track, DCC track power supply remains constant whether a train is running or not.

Mobile decoders must remain in constant communication with the DCC system’s command station to receive digital packets embedded in the track power supply and to be able to draw on that power to operate on-board lights, sound and of course, the motor.

Locomotives used for shunting operations benefit from Stay Alive, particularly those with a short wheelbase and few wheels such as the Hatton’s Andrew Barclay 0-4-0ST or the Hornby ‘Peckett’ of the same wheel arrangement.

The weakness inherent in model railways – the supply of power through the rails – is also their biggest asset. While it’s a great way of getting power to our trains, it does rely on a good contact between locomotive wheels and the rails to conduct current well for both traditional analogue and DCC.

Digital information needed by decoders is communicated via the same route, and the same applies to the method of transmitting current from the wheels to the internal electronics of a locomotive. Dirt on the rails and poorly aligned current collection pick-ups will interrupt power and data transmission, causing poor running and flickering lights when they should be constantly illuminated. Keeping the track clean (no more than is required on an analogue layout) and good maintenance will overcome most contact issues.

DCC-users can take further advantage of another feature that draws on the fact that track current is always available to a decoder: ‘Stay Alive’ or ‘Keep Alive’. The principle is simple, and has come more to the fore among modellers who wish to focus on fine running and accurate slow-speed control of their models, particularly smaller locomotives which will be lighter, and will have fewer wheels from which to collect current.

For the full article and more images, see the June edition of Modelling – available now!

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