Abstract: Apparatus for detecting ferromagnetic debris in a fluid medium in a container includes a plug attachable to the container and having an associated magnetic field preferably produced by a permanent magnet. The plug is at least partly exposed to the fluid to capture debris in the fluid. The apparatus further includes a portable sensor for optically sensing the captured debris, with the sensor having a probe that is connectable to the plug. A method for using such apparatus is provided, and in general a method of detecting ferromagnetic particles in a fluid medium in a container includes the steps of: a) magnetically capturing particles from the fluid using a plug with the container, and b) interrogating the plug with light for captured particles using a portable probe.

Abstract: In apparatus for controlling the supply of power from an alternating current electrical supply of at least three phases to a resistive load, the load is so arranged that there exist current paths both between each phase connection of the load and two adjacent phase connections of the load and between each phase connection of the load and a common point which is directly connected to the neutral of the supply. The switching means for connecting each phase of the load to the corresponding phase of the supply is arranged to change from a non-conducting to a conducting state only when the voltage across such switching means is substantially zero, and to change from a conducting to a non-conducting state only when the current through each switching means is substantially zero.