Abstract: A detector includes a board with a connector, a measurement resistor, a switch, and circuitry. The board with the connector is coupled to an external board. The measurement resistor is connected to the connector. The switch is connected to the measurement resistor and switches on and off an electric current flowing thorough the measurement resistor. The circuitry measures a potential difference between both ends of the measurement resistor, and determines, based on the potential difference measured, a coupling state of the external board with respect to the connector. The circuitry controls the switch to switch on and off the electric current flowing through the measurement resistor.

Abstract: An electronic toll collection (ETC) system has a problem that the system cannot issue a receipt at the time of use, because the system permits an ETC vehicle to pass a tollgate nonstop. The invention intends to solve the problem and provides a receipt-issuing device while ensuring security. In order to achieve it, the receipt-issuing device includes an IC card interface unit through which information is read out or written to an IC card, an SAM unit that enciphers information to be recorded in the IC card, and deciphers information to be read out therefrom, an operation unit that inputs an instruction of issuing a receipt, a printer unit that prints the receipt, and a control-processing unit that, when the SAM unit verified the security, permits an issue of the receipt by the printer unit. A requirement in the ETC history of use that the receipt is once issued is erased from the IC card, or the requirement is locked on data so that the receipt cannot be issued again to the same requirement.