Originally Posted by: TEEWolf 
Well, this is an interesting type of running a layout. Running locos analogue and the devices dgital! An "overlay" is not enough. You have to be very carefully seperating both typs of electric supplies. And you are loosing all advantages of a digital layout, like running several locos at the same time only with one controller. This is in analogue mode impossible, except you are using a catenary system and even then you need 2 controller for only 2 trains. I had such a layout running about 50 years ago too. I think it is pretty superseded. In the 21st century I decided to go digital, although I still do have this analogue layout including the M-tracks.

Actually, my way of running the trains is identical to Martti´s, EXCEPT that my digital control consist of PLCs instead of an ECOS, CS or Intellibox. And instead of ROCRAIL I use my own software.
So, the way my ANALOGUE trains are run, is by turning track-power on and off with industrial 24V relays. In some sections (before and after signals mostly) different voltages are switched in by the relays from different trafos.
The limitation is, that there can be only 1 trains in each section. How many trains do YOU run in each section? -Actually, you should never ever run more than one, just as in real life ;-)
My running concept is NOT about running X trains with X controllers.
My system runs a lot(*) of trains automatically on the main line.
I am restricted to run a small shunter on the side areas of the station. I can move locos around in the BW area, industrial area, etc...
I can make up trains at the station, and get them ready for main-line running. I then push a button, and wait until the system will allow me to "insert" it into the automated mainline, once this is free.
The manual part of the startion is divided into 5 sections, and the (only) two manual trafos/controllers that I have for manual running are assigned to these sections using Z-Schaltung.
JUST because a system is "analogue" does NOT mean that it is "simple" or identical to what you ran 50 years ago. It is a highly sophisticated system stretching the boundaries of analogue running into that of digital running. At the cost of more cabling and a lot more cutting and isolation of track sections.
Electrically my system is VERY robust; Relays are 24V with a failure rate of approx. ZERO, and the 0 of the 24Vdc is bridged to the 0 of the 16Vac track trafos, thereby allowing excellent use of isolated rails for 24V feedback.
The flimsy märklin solenoids are driven with 24Vdc too, giving much more torque. (Pulse is limited to 0,1s, and in 12 years none have burned. End-cutoff-contacts has been bridged, and so far none have failed! (knock-on-wood))
(*) Definition of "a lot"; The theoretical MAX would be around 8 trains actually MOVING at once, but that is crazy, and the normal is around 4. These are all run automatically between 2 shaddow-stations that allow the automated system to randomly select among 30 trains. (I am not counting branchline automation and shaddow-stations here!)