A switch device includes a switch operation unit to be mechanically operated so as to be in on or off state; a detecting unit configured to detect whether the switch operation unit is in the on or off state; a first mechanism to be configured to close electrical contacts of at least one circuit when the switch operation unit is operated to be in the on state; and a second mechanism configured to maintain the electrical contacts in an closed state and switch the electrical contacts to an open state in response to electrical signals indicating off, on, and, off to be received sequentially while the switch operation unit is in the off state.