A system configured to provide cooling of electronic equipment in a shelter in combination with an air conditioning (A / C) system. The system includes one or more blowers for drawing air into the shelter, a damper arrangement for controlling air exhaust. The system further includes a DC powered controller coupled to the one or more blowers, the damper arrangement, and the A / C system. The controller is configured to receive at least a first analog input signal associated with a shelter-interior temperature, a second analog input signal associated with a shelter-exterior temperature, and a plurality of alarm input signals and to generate the one or more first control signals to control blower rotational speed, the second control signal to open / close the damper arrangement, and a third control signal to inhibit / activate the A / C system based on at least the first analog input signal, or the second analog input signal, or a plurality of alarm input signals, or a combination of these.