[user18]

I have some 3.5mm connectors with 4 conductors. I know there's left, right, and ground. But what does the fourth one do? I've read that the fourth is used for video, then on another site, it says it is used to supply additional power. So I'm guessing the actual usage is dependent on the application.

My question, is it safe to just leave it as-is? They are CP-43502PM-ND from Digikey.

 

[ayt999]

what's your application? if you are using it as a 3-conductor substitute you may need to connect the fourth conductor to ground depending on the female connection you use it with, but otherwise you shouldn't have any issues....

 

[MisterX]

Quote:

I've read that the fourth is used for video, then on another site, it says it is used to supply additional power. So I'm guessing the actual usage is dependent on the application.

Excatly.
You don't need to connect pin 3 to anything if you are using it for a typical trs audio connector

 

[balou]

you could build a fully-backwards compatible balanced headphone jack