Hamamatsu Corp. has reduced the power consumption of its H9858 photomultiplier module by more than 90% and its weight by a third. The photosensor now can be operated for more than 1000 h on two AA batteries. The internal high-voltage power supply can be remotely programmed, enabling computer control of the module’s gain and dynamic adjustment of signal gain based on the detected light level. The module is designed for direct mounting to a printed circuit board, and a fiber optic connector is optional. The H9858 can be obtained with spectral sensitivities from 185 to 920 nm, and a photon-counting, P-type model is available for low-light measurements.