How to connect the Arduino with the BIS-411 switches and relays in a star?

Current state: existing electrical installation made in star, bell switches, BIS-411 24V relays in the cabinet.
Purpose: addition of budget automation in the form of Arduino (MySensors) with retention of functionality, i.e. operation of switches in case of Arduino failure.
Questions:
- how to reconcile Arduino and relay input voltages? (replacement with another type?)
- how to connect the switch to short-circuit the Arduino and relay inputs at the same time?
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t4l3rz3 wrote:

- how to reconcile Arduino and relay input voltages? (replacement with another type?)

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As in the diagram shown.

t4l3rz3 wrote:

- how to connect the switch to simultaneously short the Arduino and relay input?

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The simplest way to do this is to make sure there is no failure. With a correctly designed circuit, the probability of the control system failing is very small, much smaller than the probability of the relay failing. So there is little point in duplicating the function of the control circuit.