A lighting apparatus is disclosed herein that may illuminate a space with light emitted from a light source or to concentrate the emitted light on a certain object. A method and apparatus of the invention permits separating ions of different mobilities by passing them through an abrupt change or step in electric field magnitude. An additional roll is disposed adjacent to the folding roll and is rotatable about an axis in a second direction at a second roll speed. The taxpayer’s employer can provide its employee’s tax information electronically. For example, the peak detector can reduce a discharge current in response to an increased charging current and increase the discharge current in response to a decreased charging current. A frequency mixer according to the present teachings includes a set of mixing devices that generate a first sum signal and a second sum signal in response to an input signal and a drive signal such that the first sum signal is out of phase in relation to the second sum signal.