In an envelope comparison embodiment, a delay calibrator produces a delay signal based on a comparison of a feedback signal and an envelope component of the transmitted signal. The lensing structure is positioned in the LED lamp so that emitted light from the LED die excites the phosphor layer. The head restraint includes a bun moveably attached to the post assembly, a first gear, and a motor that rotates the first gear in a clockwise or counter-clockwise direction.