The G4EB2 brain replaces a B4 brain on a G4PB32H or PB32HQ rack. The G4EB2 is an Ethernet-based 32-channel digital brain that uses the OptoMMP protocol. Using the G4EB2 as a replacement for a B4 brain, you can upgrade older G4 and Quad Pak I/O to Ethernet-based I/O. Because this brain is compatible with the SNAP PAC System, you can use the upgraded I/O unit with current SNAP PAC controllers and PAC Project software while leaving I/O and field wiring intact.