MBP 2015 Lib - Supply Pad Explanation

[Chris]

I have been using the Gaussmarkov lib for Eagle and would like t move over the the MBP2015 lib.
Can someone explain the pad labels for the IO Supply Pins in the 2015 lib please?

Here is the label.
G L S + - I R O

Here is my best guess on this:   
Ground, L, S, +(+9v), -(-9v), Input, R, Output

Thanks!
Chris

[madbean]

Ground, LED wire to 3pDT, Send (FX In), LED+, LED-, Input, Return (FX Out), Output

[Chris]

Thank you, Brian! Appreciate the quick response