The ST100 is comprised of a solar cell energy source, an energy reservoir, analog and digital sensor connections, a microprocessor for sensor control and a radio transmitter, all packed into a 0.8-by-1.6.-by-0.4-inch footprint. Designed to operate indoors, the device requires 200 lux (typical of building hallway lighting values) to generate energy. The vendor claims fundamental breakthroughs in the creation, storage and management of power. Within the ST100’s two-stage solar cell, one stage provides quick startup energy while the other charges an onboard energy reservoir. It can store sufficient energy to operate continuously for five days in complete darkness. Each module also assures reliable wireless communication via sophisticated RF protocols, says the vendor, including multiple broadcasts, fast data rate, error detection and unique addressing. The STM100 is available in OEM quantities for less than $25.