Abstract: A manhole cover is seated on a flange in a frame from which depends a skirt forming an access opening to a cavity. A cover lifting mechanism external the access opening includes an arm secured to the cover and a tubular cylinder fixed to the skirt, the cylinder including internal aligned journal bushings. A tubular shaft depends from the arm into the journal and axially displaces and rotates about the journal axis. The shaft has an axially extending central bore with a threaded portion. A threaded rod in the central bore rotates about the shaft axis and is captured to a bearing secured to the cylinder lower end. The rod upper end is squared to receive a socket wrench for manually turning the rod with a mechanical advantage which lifts the shaft, the arm and thus the cover out of its seat. Once lifted, the cover is readily rotated away from the access opening by rotating the shaft in the journal while the threads remain engaged.

Abstract: An improved instantaneous floating point (IFP) amplifier is provided having a plurality of cascaded amplifier stages, with each stage having a plurality of possible gains. The input sample signal is passed through each stage so that no stage is selectively bypassed.A bipolar, logarithmic amplifier is used for gain control. The gain control bits correspond to the industry standard gain control codes, thereby eliminating the need for bit mapping.The offset voltage control circuit is initialized during power-up by removing the IFP input signal and measuring the input referred offset at each gain setting. The measurements are stored. When a sample signal is received at the IFP amplifier input, the appropriate gain is applied to that signal along with the stored offset value corresponding to that gain.