Amp plug wire question poweron

[Cunningr]

Been looking at the amp wire diagram but I am unclear which connection is switched on that can be used to tell aftermarket amp the radio has been turned on.

If anybody can help appreciate it. I am wiring up my aftermarket amp interface plug now. Took cheap ebay amp big plug off of board. Going to use the tin amp cover flipped reverse and bolted to extra factory amp brace. All interconnects will be on here, with the plug out end where factory amp plug is located.

When i get it all together will post pics and a wiring diagram.