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Questions relating to designing PCBs
By AntoniosHadji
#188192
I'm looking to create a simple circuit but I'm not sure where to start. Exact answers as well as references to where I can find this information on my own are welcome.

The use case: I have two thermostats (24V) which are basically switches, let's call them A & B. I want to create a device that I can connect by wire that will not allow B to switch on while A is on or will shut off B if A turns on.

A & B both have two wires so the input is four wires. The output needs four wires as well.

states
A & B both off : nothing to do
A switches on, B is off: Switch on A.
B switches on, A is off: Switch on B.
A is on and B switches on: the device does not pass through signal from B, A continues to be on. When A switches off, B is turned on if still on.
B is on and A switches on: B is shut off and A is turned on. B will be turned back on after A shuts off if it is still on.

Put another way, A is always given priority and and only one circuit is open at a time.

Thanks in advance. And if there is a better place to post questions like these please let me know.