Risk of inadvertent introduction of software bugs to a large number of users during a software update is minimized using an automatic mechanism controlling update release. The power supply rejection circuit generally comprises a comparison circuit for comparing a signal associated with a power supply such as, for example, a Wheatstone bridge configuration, to a stored reference voltage, such that the comparison circuit includes at least one existing capacitor therein. A method involves moving a viewing instrument to or from a position near an optically transparent portion of a blunt, enclosed distal shaft end and a proximal side of an enclosed working area.