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Schmitt trigger offset voltage

I found this circuit which generates an offset voltage to the hystersis (so the threshold voltages are for example not -3V and 3V but -2V and 4V).

It would be the same as if you remove R1 and put a voltage source between R2 and GND, right? The circuit above just realizes that?

How does this exactly work and how can I calculate the resistors? I don’t understand how it works with R1. The voltage where R1 is connected to is the same as the positive battery voltage of the op-amp. The output will change between 5V and -5V.

For my logic, 2.5V should drop on R1 and 2.5V on R2. However, there are also 5V (or -5V) that need to drop on R_hyst and R2. How does that work? What will be the final voltages and how to calculate it? An explanation would be awesome.

Thank you

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