The H7467 is a photon counting head designed for photon counting by simply connecting to a PC (personal computer). The H7467 houses a metal package photomultiplier tube, high-voltage power supply circuit, photon counting circuit, 20-bit counter and microprocessor in a compact package. Data transfer, measurement time and other necessary adjustments are controlled by commands from the PC through the RS-232C interface. The photon counting circuit discrimination level and the high voltage supply for photomultiplier tube are preadjusted to optimum levels prior to shipment so that the H7467 can be easily operated by simply supplying +5 V.