Abstract: An instrument with an illumination ring that edge-lights an opaque dial face with increased light flow by augmenting the conductivity of both the light receiving portion of the ring and a bevel for deflecting light laterally across the face. The increased light flow is accomplished by an extended annular wall portion spaced from the edge of the dial face.

Abstract: A vacuum switch in which the diaphragm movement with increasing vacuum is opposed by two springs which determine the vacuum required to actuate the switch. As the vacuum subsequently decreases one of the springs is rendered inoperative before the switch resets so the reset vacuum is determined by the one spring remaining effective. The spring which is rendered inoperative is compressed between the actuator and an eyelet which can seat on the actuator (spring ineffective) or the housing (spring effective) and which also functions to limit motion of the actuator relative to the eyelet so the switch operated by the actuator cannot be overstressed.