what is a "field relay" ?

[ima71 trucks are older]

I need to replace the charging harness on my 1969 F100 (it's completly fried)

The wiring diagrams on this site show a field relay in the system. This diagram for normal 1965-up alternator shows no such relay. will a charging system wired like this work?
I'll be using a new stock alternator and a new voltage regulatior

[68F250]

The field relay is inside a normal alternator regulator, you don't see it.

The high-output alternator/regulator breaks out the field relay into a separate component. Look at another wiring diagram for the charging system, not the 65 Amp diagram.

[ima71 trucks are older]

thanks, I got it wired up.