Photomultiplier tubes (PMTs) are used to detect faint optical signals from weakly emitting sources. The photocathode uses three or more kinds of alkali metals. Compared to avalanche photodetectors (APDs), they offer significantly larger active areas. These PMTs are controlled with an included software package designed for use with 64-Bit Windows® 7 or 10, which provides a GUI for adjusting gain, output offset voltage, and bandwidth..