... sources. 3. 3 incoming and 1 outgoing Auto Generator Transfer Switch (ATS)1. 3 incoming + 1 ... single phase.- The 1st come from the national network (MAINS),- The 2nd come from the local area generator ... .No. 2 to the local area generator (AG ) , when (MAINS) doesn’t exist, and even if (HG) exists ... when both (NN) & (AG ) don’t exist. 3 - Consists of :A - power relays, B - metallic box, C - connectors ...