Alternator wiring question

Hi all,
I have a JDM OBD1 alternator on a JDM B16A and would like to know what the White/red alternator wire does?
I understand the Black/yellow goes to ignition and the White/blue goes to the charge light but what does the White/red wire do?
I am fitting an aftermarket ECU and need to know if it is required and if so what it actually does.
Attached is a diagram but it doesn't list the White/red wire for some reason.
http://uploads.tapatalk-cdn.com/2016...afab8d33f2.jpg

Wht/red is Alternator FR Signal - sends a signal to ECU when the alternator is charging


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Thanks dorikin. I couldn't tell if it was control or FR. Cheers