1000Base-T (also known as Gigabit Ethernet or Gig-E for short) employs all four pairs in the RJ45. Further, each pair is run in duplex mode which means it is both transmitting and receiving data simultaneously. In many ways this greatly increases the complexity of the interface. While Gig-E systems can deliver 1000 megabits per second in each direction, these interfaces are still backwards compatible with the 10Base-T and 100Base-TX systems. When connected to one of these earlier systems, only the channels shown in a red highlight will be active and the data rates will be automatically slowed accordingly.