Confusion about Line in/out pins on Audio board

[cosmictea]

Good morning,

Just had a quick question about the audio board line in and line out. I've been looking for resources in how to build a line in / line out connection, particularly like the one in the following link, under "Optional Add Ons":

http://www.pjrc.com/store/teensy3_audio.html

It looks like on the board there are 4 connections required for a line in and 5 connections for a line out. On the shield the connections are labeled as R, L and G. This is right, left and ground I assume. For the line out connection, why are there two holes for the L and two for the R? I don't see a connection for the two extra holes above the L and R so I am assuming these two extra holes don't do anything? Is this true?
Thank you!

 

[Frank B]

It's a std-connector as used in PCs.

 

[cosmictea]

It's a std-connector as used in PCs.

Ok sweet. I have seen those before and will check them out. Thanks!

 

[PaulStoffregen]

I don't see a connection for the two extra holes above the L and R so I am assuming these two extra holes don't do anything?

Correct, those holes aren't connected.

On PCs, those pins are used for the switches in the headphone jack. That's how plugging in a cable or headphones to your PC can cause the speakers to turn off. The audio shield doesn't use those pins.

 

[cosmictea]

Ok that makes perfect sense. Thank you guys for the help