My specifications

It is a question of replacing the old Fulgurex motors, of which here is the wiring diagram for one motor…

Older diagram with Fulgurex motors

… with servos controlled by a dedicated decoder, without modifying the control logic contained in the Zelio programmable module:

New diagram with servomotors

Don’t panic! In fact, there is not much changed. There is simply the XbusTCO borad which makes it possible to translate the state (or rather the state change) of the Zelio outputs in commands comprehensible by the LZV100 DCC command station (which already existed, although I did not represent it on the first diagram), and the Switchpilot Servo decoder. And these commands now transit through the track, or more precisely via the feeder which feeds the track, in the form of DCC signals.

The 15 V AC power supply (on the right of the diagram) is not strictly necessary: ​​power can be supplied from the track in DCC, but this is not recommended — better let all available power for the locomotives — and this solves a small problem I mentioned before, about the sound emitted by the servos at the stroke end. Indeed, you simply momentarily cut the power to stop this noise. How does it works? I don’t know, but it works!

Therefore, a simple pushbutton with a normally closed contact (NC), placed in series in the 15 V AC cable, does the trick. You simply have to actuate it after some turnout maneuvers, when the whistling becomes too painful!