In a passive PoE system, the injector does not communicate with the powered device to negotiate its voltage or wattage requirements, but merely supplies power at all times. The common 100 Mbit/s passive applications use the pinout of 802.3af mode B (see )with DC positive on pins 4 and 5 and DC negative on 7 and 8 and data on 1-2 and 3-6. Gigabit passive injectors use a transformer on the data pins to allow power and data to share the cable and are typically compatible with 802.3af Mode A. Passive midspan injectors with up to 12 ports are available.