Abstract: An electrical frequency responsive circuit comprising a first coil constructed of wire having an insulating coating thereon wound in a single layer about an axis of generation, and a second coil, also constructed of wire having an insulating coating thereon wound about an axis of generation in a single layer, said coils being axially related and having diameters and/or pitch to provide inductance and capacitance between the coils which is at least initially adjustable whereby the circuit is responsive to an electric signal having a predetermined electrical frequency imposed across the coils to provide frequency band suppression about the predetermined frequency.

Abstract: An electrical frequency responsive circuit comprising a first relatively larger diameter coil constructed of wire having an insulating coating thereon wound in a single layer about an axis of generation, and a second relatively smaller diameter coil having an outer diameter slightly larger than the inner diameter of the first coil, also constructed of wire having an insulating coating thereon wound about an axis of generation in a single layer. One end of the second coil is screwed into one end of the first coil a distance to provide inductance and capacitance between the coils whereby the circuit is responsive to an electric signal having a predetermined electrical frequency imposed across the other ends of the coils to provide frequency band suppression about the predetermined frequency.