Ok this one is a theory on how it might be done, hoping it can be confirmed or denied..

Current layout in question is the Cortina Z scale

Area in concern is the Right lower corner, 'middle track'
(was going to put in picture but have nowhere to upload it as can only link to http)

Tracks in order as stands

8500 8588 8503 8562 8530 8530, with isolator joiner between the two 8530's
So with this a 'block' is present from the 88 to after the first 8530.
There is one light signal alongside the second 8530.

With this from what I can tell a switch controlled light stop/start using the block and an 8945 relay.



Now I think.... and this is where confirmation is required...

8500 (110mm) gets replaced with a 8503(55mm) and Circuit-8589(55mm),
this to control the 'new' signal light, and entry to the 'block'

The two 8530's (220/45) get replaced with 8531(220/30), isolator joiner, 8539(220/30), 8531(220/30)
this to control the old signal light and exit from the 'block'

I think all this can be controlled by one 8945 ?? or is two required???

Next hurdle is to work out what to connect where on the various parts and colours.

Anyone able to confirm the above is the correct way to go ?

Thanks for info on how to get an image up.

See image, the straight bits set aside is what it seems is the minimum for for an automatic train control using signals and block.

On the bit with curve attached/alongside, the red bits are parts currently in place, the green bits, the potential replacements.

So far what I have seen on many response's is...
Here are plans of actuals, very little seems to be explaining how it actually works. This latter part is what allows for understanding rather than just blindly following instructions, with understanding changes can be made to existing designs knowing the principals of how and why.

Btw in this I am helping another put together their layout, my own is of another scale (N) and has total manual dcc operation so this is me finding new depths (never know... I might get hooked to another scale)
One huge tip... second-hand track is NOT a saving... you will spend hours cleaning and fixing...