Abstract: A read-write optical disk with method of manufacture and configuration of writing mechanism. The optical disk is fully configured at every readable location with pits filled with a stable, cyclable, solid-liquid (or solid-fluid) phase-change material, such as a paraffin mineral oil fraction, having a specific reflectivity when in the solid state, and a layer of a particulate metallic material capable of being magnetically attracted or repelled and having a reflective value significantly different from that of the phase-change material. The writing mechanism includes laser light amplification means to provide sufficient heat from the laser, which is used in the reading mode, to effect the solid-liquid phase change. The writing mechanism further includes a material-moving magnetic element. During operation of the write cycle, the phase-change material, in selected pits, is fluidized and is in the fluid state while a magnetic field is applied to the pit area.

Abstract: A system for measuring electric power supplied through a power distribution network and, inter alia, detecting theft of power from the network, and a remote reading Hall effect based electric power meter for use therein are both described.