Okay, the original question about stay alive caps is a bit complex. As I mentioned before some manufacturers use an auxiliary capacitor board to keep engines alive while crossing dead track spots.
Here's how a friend of mine in Germany describes how a Lenz Gold Decoder can still operate with power interruptions...
"The Lenz Gold decoders have something they call USP or Uninterrupted Signal Processing. I have visited Lenz when I was developing support for them on my app, and they gave my a demo on their test layout. A small two axle engine drove on to a piece of paper (A4/letter format) which was across the track. On that piece of paper, it stopped, reversed and back away from the paper. Very very convincing demo."
"There’s no magic to it. Bernd Lenz, the owner, is just applying math to the problem. When the wheels are separated from the track, the wheel/paper/track combo behaves like a capacitor. In that case, the edges of a normal DCC signal are electrical spikes, so in the decoder they detect the positive and negative spikes and reproduce a perfect DCC signal. Very clever."
