To start I've adapted the ESPhome code from this excellent project - https://frenck.dev/diy-smart-doorbell-f ... -2-dollar/
How best to detect button presses given this setup?
How can it be adapted to work best?
But the big difference is that the bell presses need some voltage and current through them to fire the indicators (solenoid hits the flag frame). +8V goes into the board goes round the circuit and exits to the bell unit.
The original bell needs 8V to work and I've had a 8V DIN-mounted feed from the CU into the bell unit. I've soldered up a buck step-down converter from 8V-5V.