Whatizzit?

Gonna paste a link first...its a DAC I have but cannot seem to get working...the ESS Sabre stuff is my favorite sounding DAC...however on this device there's a little "led" looking relay? right behind the Spdif input (pink input on left hand side bottom) an right before the crystal clock...I want to test it...maybe replace it...have no idea what it actually is or does...it labelled "U6"...nothing on any of the other schematics (the one schematic I need is no longer available)...

Forgive my SMD lack of brains here...

https://hifimediy.com/wp-content/uploads/2020/03/s1.jpeg

Hifi.me dac...


Same part as this labelled "U1" here:

https://hifimediy.com/wp-content/uploads/2020/03/IMG_0089_recompress.JPG

I got the DAC to work...bad optical cable...still would like to know whatizzit?