Raincheck is a simple fully automatic roof vent controller; it is the size of a ‘one gang’ electrical fitting and comes complete with a rain sensor.
It is operated by means of a rotating knob which is graduated to reflect temperature. Select the temperature you require, and the controller will open and close the vents to try and maintain the selected value, if it rains the external sensor will shut the vents.
For manual operation, turn the knob fully to the left and the vents shut, fully to the right and they are open.