What is the anti-arc clip used for in the mainframe?

The clip is used to inhibit the triac from outputting any power until the module is fully inserted into the mainframe. This will assist in preventing arcing of the gold fingers when the controllers are accidentally inserted or removed while the power is turned on. The clip is installed in the 3rd position of each of the white edge connectors in the mainframe. Newer anti-arc equipped modules will not output any power until this anti-arc clip is installed in the mainframe. All mainframes built after January 1999 have this clip already installed in them.