A wooden dark box was initially constructed for the a hybrid photo-diode (HPD) module DEP PP0350. A pulser was installed on the opposite end of the box composed of a fast LED driven by a pulser circuit shown on the right. | A wooden dark box was initially constructed for the a hybrid photo-diode (HPD) module DEP PP0350. A pulser was installed on the opposite end of the box composed of a fast LED driven by a pulser circuit shown on the right. |