Help identifying unfamiliar pad labels on Effects Layouts PCB

[geoffrey]

I recently came across this Effects Layouts Test Rig Mk III board in my pile (can't remember when I bought it ) and when looking at it I realized I've never seen some of these labels before, particularly the pads where you connect the PCB you'd like to test. Can someone please help define these for this donkey? I emailed the dude from Effects Layouts and he never responded, so now I'm coming to you guys.

Forgive my ignorance. Even though I've built a ridiculous number of pedals, I again show myself for the charlatan that I am

See image below: SND, RTN...are these the same is "In" and "out"?
And what is L+ and L-?

 

[szukalski]

I have one of these. The top middle pads are the ones you connect to sockets. They are the ones which connect to the board you're testing.
SeND -> Board In
Board Out -> ReTurN
GrouND -> Board ground
L- -> Board LED -
L+ -> Board LED +
+9V -> Board 9V

 

[geoffrey]

I have one of these. The top middle pads are the ones you connect to sockets. They are the ones which connect to the board you're testing.
SeND -> Board In
Board Out -> ReTurN
GrouND -> Board ground
L- -> Board LED -
L+ -> Board LED +
+9V -> Board 9V

Thanks a million, Dave.