So I did some investigation. The open port in the photo looks like the obvious place to plug a reed switch into. Unfortunately, I don't have a plug that will fit into the port. Also, there are three prongs in the port. A reed switch only requires two wires. I'm more confused. Is there an LGB part number for the proper cable to use here ?
For preference, that port is designed for a Hall-Effect sensor, which uses three connections.. These are available from Marklin/LGB or Massoth, and just plug in to the sound module.
The other end of the cable is a small circuit board, which would slot into an LGB motor-block. there is also a ring magnet to fit on the axle. - You have to remove a wheel for this.
The other port (again, three wires) is for reed switches to be triggered by track magnets. - Usually used for whistle/horn and bell.
I am trying to find a full service manual for the 6500n series of sound cards, to see if the unit will accept a signal from a reed / magnets, but no luck so far.
So your talking about fitting the "small circuit board" to a locomotive axle. Can I fit it to a trailing car axle instead ? Would you happen to have a number or link the the Hall Effect Sensor ? Again, would it work on a trailing car ?
The socket with the bell and whistle pix above are for reeds for bell and whistle. Middle pin is common to both reeds. Wagon wheel socket is chuff which originally was only to be used for steam engines.
It might be a little 'off' and perhaps too far away? - Black-bit in-line with magnet, and perhaps a little less gap?
We any also be a a point where you need a local, tame DCC user?? - I fear a CV will need changing.. Just need to find the 'damn-paperwork'..
T'would appear to be CV 64, but the paperwork, so far, is less than helpful..