A band-pass filter is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range. An example of an analogue electronic band-pass filter is an RLC circuit (a resistor–inductor–capacitor circuit).
A filter that attenuates signals both below and above the desired passband.
An electric circuit designed to pass only middle frequencies.
Having the shape or form of a helix; spiral
(A-helices) A common motif in the secondary structure of proteins, the alpha helix (±-helix) is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier (hydrogen bonding).
A helix (pl: helixes or helices) is a type of space curve, i.e. a smooth curve in three-dimensional space. It is characterised by the fact that the tangent line at any point makes a constant angle with a fixed line called the axis.
coiling: in the shape of a coil
helical walkway
City Hall in London has a 500m helical walkway ascending the full height of the building. Very well photographed by pretty much everyone who entered the building.
Helical Circuit (01)
Schematic 3D model of continuous helical conveyor system using two helical stacks in an offset configuration.