I have found this schematics generating a band stop filter design:

The corresponding transmission is this here:

You see that this design generates a band stop at around 230Hz.

I have tried to find a similar topology in books and online but was not successful. Do you have any idea what this is? And if so, how to calculate the band stop frequency and width?

Thanks in advance for your help!

Philipp

P.S. I hope that I used the correct subforum. If not, please let me know!