Ratio Detector

[gabrigam66]

Hi,

 

 

I built the attached ratio detector circuit and it works. but I can't understand the reason for the connection marked in green.

I need an explanation, please.

Thanks in advance

 

GR

[HarryA]

The vertical green line supplies current to the transistor. The other part of the  green line supplies  current to the detector which modulates it to form the audio and afc outputs.