A mechanism, of a camera, for surely resetting a microcomputer at time of switching among a plurality of types of power sources. In the mechanism in which a manual operation dial for switching among the plurality of types of power sources is rotated to slide an electrical contact piece over a predetermined electrically conductive/non-conductive pattern so that a desired power source type is selected, an electric conductivity/non-conductivity between an IC and a negative terminal changes, immediately before an electric power across a positive terminal and the negative terminal is changed from "ON" to "OFF", and immediately after the electric power is changed from "OFF" to "ON". In association with the change, the IC outputs a reset signal to the microcomputer of the camera.