We use this apparatus for timing the output of electro explosive devices (EEDs). We attach a fiber optic cable to each EED, as we show in the photo above, at left. The sensor module has two fiber-optic inputs, as we show in the middle picture. The sensor output shows the times when the two EEDs fire, as we show in the upper oscilloscope trace, at right. The lower oscilloscope trace records firing current from a capacitor discharge.