What does B+ B+ B- B- mean in terms of RS485

If you were to hook up B+ B+ B- B- to talk RS485 with a PLC that has an RS485 port with A B SG how does that work? I am use to working with TX RX RTS CTS SG not with Bus type RS485

I had an earlier post that nobody responded to that explains the exact application...I have talked RS485 many times with many devices...And it wont be a 4 wire connection...Look at my post from earlier this morning...its basically talking modbus RTU between a Totalflow XFC 6413 and an Idec Microsmart prenta PLC...RS232 is working...but I dont understand B+ B+ B- B- on the Totalflow board.

RS485/422 channels are usually marked. Tx+ Tx- Rx+ Rx-

RS422 is the four wire version of RS485 though they are often both referred to as RS485. When you are connecting as a two wire system the +'s go together and the -'s go together.

They might be having the extra terminals as a way to make chaining devices easier. The letter B for the second channel maybe?

A+, A- and B+, B-

Some even go another step: