Two different styles of switches are used under this part number. Although slightly different, they are completely interchangeable. The transformer leads (plugged onto terminals 1, 2, 3, and 4) plug onto either switch in the same positions. The 120 volt input lead to the switch plugs onto terminal "A" on switch STYLE 1 and either terminal "A" or "B" on switch STYLE 2 (terminals "A" & "B" are COMMON on switch STYLE 2). Style 2 is the current configuration.