An apparatus that includes a rotor blade assembly capable of generating vertical lift, one or more propulsion units capable of engaging and disengaging from the rotor blade assembly, an encapsulating housing, and where the encapsulating housing is capable of containing the rotor blade assembly. SCS-OCV introduces complex variation concept to resolve the blocking technical issue of combining local random variations, enabling accurate calculation of statistical variations with correlations, such as common-path pessimism removal. The referral card has a referrer identifier which identifiers a referrer of a holder of the referral card. The ramp-from-mute operation includes ramping the output of the audio output circuit from the reference dc voltage offset to a dc voltage offset associated with the second of the pair of audio signals. In a lifted position, the inflection point approaches the back wall for gripping the tool therebetween. \u201d The neurological control system generates neural modulation signals delivered to a nervous system component through one or more neuromodulators to control neurological state and prevent neurological signs and symptoms.