Automatic transfer switches (ATS) continually monitor the incoming utility power. Any anomaly such as voltage sags, brownouts, spikes or surges will cause the internal circuitry to command a generator/UPS startup and then a transfer to the emergency generator/UPS when additional switch circuitry determines the generator/UPS has the proper voltage and frequency. When utility power returns, or no other anomalies have occurred for a set time, the transfer switch will then transfer, back to utility power and command the generator/UPS to turn off after another specified amount of "cool down" time.
