An inspection system for assemblies, especially for flash units of used film packages as to if the flash units are reusable. The inspection system circulates pallets each holding a flash unit in a predetermined posture around a plurality of inspection stations for various inspection items. Inspection data detected in each inspection station is written in a memory of the pallet through a data communication system disposed in each pallet and each inspection station. A computer reads the memory for classifying the flash unit on the basis of the inspection data on all inspection items and writes classification data in the memory. A plurality of electrical inspection apparatuses are disposed in the inspection system for simultaneously inspecting electrical properties of a plurality of flash units. Each inspection apparatus has proving pins, an actuator and a photo-sensor which are moved into their operative positions when the pallet holding the flash unit is stopped at the inspection apparatus, wherein the inspection apparatus charges a main capacitor with a high D.C. voltage while measuring the voltage of the main capacitor.