The HP 0604-001325 photo-interrupter sensor is a replacement part for printer sensing systems. It is identified as a photo interrupter, a component used to detect paper as it moves through a printer.
The Samsung service manual assigns this part number to several paper detection positions, including registration, feed, paper-empty and exit sensing. The specific position depends on the printer assembly where the sensor is installed.
A distributor lists this part for the Samsung ML-4510 and ML-5010 printers. The part number is 0604-001325.