The ATS612JSB dynamically-coupled gear tooth sensor is a peak detecting device that uses gain control to provide extremely accurate gear edge detection down to low operating speeds. Each sensor subassembly consists of a high-temperature plastic shell that holds together a samarium-cobalt magnet, a pole piece, and a dynamicallycoupled differential open-collector Hall IC that has been optimized to the magnetic circuit. This small package can be easily assembled and used in conjunction with a wide variety of gear shapes and sizes.