A breath alcohol measuring device is provided with features for superior handling especially of the replaceable mouthpiece. A key exchange initiator packet that does not include a key to be established is sent from an initiating device to another device via a network. The negative electrode active material layers are composed of an alloy containing silicon, which intercalates and deintercalates lithium, and iron, which does not intercalate or deintercalate lithium. The sensor boosts the first voltage to a second voltage in response to the first detecting signal and generates a driving signal of a driving frequency and the second voltage. The E image information, E1, E2 are superimposed on the E image information E0, by using this relative displacement.