An interconnecting device that has sockets for printed circuit boards to plug into.
Passive and Active
Although resistors may be used, a "passive" backplane adds no processing in the circuit. An "active" or "intelligent" backplane may have microprocessor or controller-driven circuitry that adds a little or a whole lot of processing. See bus
Backplane of a Hub
Cabletron's MMAC PLUS supported a variety of networks, including Ethernet, Token Ring, FDDI and ATM. The boards plugged into the backplane, which was an intelligent device used to bridge between the various topologies. The bottom row of sockets was used for ATM, while the top row was used for all the others. (Image courtesy of Cabletron Systems.)