A series-parallel resonant LC Trap tuned to 1KHz. The upper left input signal is at the tuned 1KHz. The other circuits inputs are in 50Hz steps. Better rejection, at 1KHz, can be had by increasing the inductor to 252mH (a power of ten), and decreasing the capacitor to 100 nF (a power of ten), but at the cost of widening the band of rejection.
