To provide detection technology for a package that is mounted in a physical slot and requires no power supply and that can inexpensively configure a package identification system.

The package identification system has a physical slot, through which a 1st package whose 1st and 2nd terminals are short-circuited is loaded or a 2nd package, whose 1st and 3rd terminals are short-circuited is loaded, an inversion means for inverting a received signal and outputs the inverted signal to the 3rd terminal, an output means that outputs a prescribed signal to the 2nd terminal and the inverting means, and a means that identifies which of the 1st and 2nd packages is loaded to the physical slot, on the basis of the signal outputted from the 1st terminal.