Wall switch address hardware

I have around 80 wall switches in my house. They’re combined in groups of 5 - 20 switches on 6 UTP cables. Each group makes use of one cable pair. Each switch is connected to some kind of analog address block (works like a resistor). There is an old domotic system installed in my house which responds on the signal of a switch by measuring the changes in voltage.

I’d like to replace this old system by a PLC powered system. The PLC will communicate with Home Assistant, where all logic will be.

Now is my question: how can I connect multiple wall switches on a single cable pair? What kind of system can I use for this? The PLC should be able to detect each wall switch individually.

Using only two wires, unless you have some sort of intelligence at the switch end (ie. analog encoding, CANBUS, PWM, etc.) then the only viable way to do this is analog.

Each switch is a button with a series resistor. The two leads connect as half a voltage divider. The controller reads the output of the voltage divider.

Limitations are that you can only press one button at a time.

I could use more wires. I have 6 wires available at each switch, but I don’t have a single pair from each switch to my main cabinet.
Aren’t there other options?

Would it be possible with 1-wire?

1 wire isn’t possible as at minimum you need a signal and return wire.

However re-reading your first post, it looks like they are already connected to use the minimum number of wires (2) per group via the analog method of switching in various resistors.

Your PLC would then read the analog signal from that pair. How depends on the PLC.

I’m not sure what you mean by having 6 wires at each switch, but only 2 back to the main panel.

What I meant is this: There is a cable with 6 wires going from switch to switch, but depending on the switch, 2 of the 6 wires are connected.
So in case I replace everything, I have 6 wires available.

Sounds like the analog way might be the most straightforward.

Only issue there is that it means only one switch can be active at a time on each pair.

Otherwise you are looking at putting some sort of intelligence at the switch end.