Wiring codes on Bachmann boards: (R, M+, L-, B+, L+, B-, M-, L)

[Grapevine Flyer]

I'm trying to identify what all the wires are that lead to Bachmann boards. Where the wires come in, you'll see letters like: R, M+, L-, B+, L+, B-, M-, L.  I'd like to know what those all mean. Some of them I know:

R:    Right Rail
L:    Left Rail
M+: Motor positive
M-:  Motor negative
L+:  Light positive
L-:   Light negative

I have found L+/- can be used to designate any light, and doesn't sometimes distinguish between front or rear.

What does B+ and B- stand for?

[Flare]

The boards are marked differently depending on which model you have.

Which locomotive are you working on?

[Grapevine Flyer]

I've got a number of different steam tenders. I was trying to identify the naming pattern (so I can swap out boards as desired).

[Len]

The board connections are:

R:    Right Rail
L:    Left Rail
M+: Motor Brush Connected to Right Rail
M-:  Motor Brush Connected to Left Rail
L+:  Light Positive
L-:   Light Negative
B+: Battery Positive*
B-: Battery Negative*

*Some boards allow the addition of a reed switch On/Off controlled battery pack for operation, rather than using track power.

Len

[Grapevine Flyer]

Thank you very much