| 摘要 |
A switch including an input terminal which is electrically connected in use to one pole of an electric storage battery, an output terminal and a movable contact movable between an inoperative position wherein the movable contact is isolated from at least one of the input and output terminals and a operative position wherein the movable contact electrically interconnects the input and output terminals. An electro-magnet winding is provided which, when energized prevents movement of the movable contact to the operative position and the winding and a semi-conductor diode are connected in series between the input terminal and a further terminal which in use is connected to the other pole of the battery. The diode is so orientated with respect to the intended battery connection polarity that the diode conducts to energize the winding and so prevent movement of the movable contact to its operative position, in the event that reversed polarity connections are made between the battery and the input and further terminals. |
