The ATS Mains - Mains is our range of ATS (Automatic Transfer Switch) panels for critical power applications.. The Mains to Mains ATS panel is used where the primary local utility mains supply is backed up by a secondary supply feed into the building. This type of panel is ofter used for critical loads, such as emergency fire fighting lifts. The ATS panel monitors the local primary mains supply and will transfer the load to the secondary supply if it should fail, or fall outside preset limits. An adjustable delay is included when switching from primary to the secondary supply. A key switch is included to allow manual switching between the primary and secondary supplies.