Abstract: A timer assembly automatically turns off an appliance to which it is connected within a predetermined time period after the appliance has been automatically, or manually, turned on. The timer assembly includes a three-position selector mechanism with rotating cams that activate a plunger to control the operation of an electrical switch which, in turn, activates or deactivates the appliance. Rotation of the selector mechanism is controlled by a clockwork assembly which rotates the selector into a position to turn on the appliance at a predetermined set-time. When the selector is rotated into its "on" position, a gear connected to the selector engages a drive gear which is, in turn, connected to the clockwork assembly. The drive gear continues the rotation of the selector so that after a predetermined time interval, the appliance is turned off.