Abstract: A plunger is normally held in a retracted, non-indicating position by a permanent magnet against the force of a spring biasing the plunger to an extended, indicating position protruding through an indicator cap. An electromagnet is selectively energized to develop flux in opposition to the magnet holding flux, whereupon the plunger pops to its indicating position. The cap internally mounts a pair of contacts which are bridged by a plunger mounted shorting ring incident with the plunger assuming its indicating position, thereby completing an external electrical indication circuit.

Abstract: A circuit breaker is equipped with both a rotary operating handle and a power unit for selective manual and motor driven operation thereof. Mechanical and electrical control elements cooperate to insure a reliable operation in both the manual and motor driven operating modes, and, as a safety measure, to provide fool-proof, visual indications of the circuit breaker condition during the progressive stages of either operating mode. The power unit utilizes a permanent magnet, DC motor for improved performance and economies in design.

Abstract: A displacement transducer is manually applied to the cutting surface of a diamond wheel to measure the fixed reference distance and thus degree of wheel wear. The output of the transducer is amplified and directed to visual or print out devices, and archival systems. The transducer signal may be transmitted to provide central processing of field measurements.