The transfer switch senses when utility power is interrupted, and starts up the generator if the utility power remains absent. In about five to ten seconds, when the generator is producing full power, the transfer switch disconnects the load from the utility and connects it to the generator, restoring electricity to the load. The transfer switch continues to monitor utility power, and when it is restored, switches the load from the generator back to the utility. Once the generator is disconnected, it goes through a cool-down routine and is automatically shut down.

ASCO manufactures several types of transfer switches. ASCO's automatic transfer switches are designed to be simple to monitor, operate and maintain. All controls needed for daily use are conveniently located on the front door, where bright lamps indicate the switch position. All components are front adjustable and front removable for optimum serviceability. As an extra measure of safety and quality, ASCO's transfer switches are UL Listed by Underwriters Laboratories for use in emergency power systems. They are also CSA certified by the Canadian Standards Association.